The aim of this thread is to revive a long domant 1940's RCA TV without the shotgun replacement of parts. I will only change what is absolutely necessary to get set running in excellent and reliable shape.

I acquired an RCA 721TCS 10" table model receiver in 2013. I was told by the seller that it had been his parents and the set had been relegated to the attic in around 1960 where it remained unpowered for 60 years. The seller said he hadn't dare plug it in.

Upon getting it home I immediately pulled the chassis to find an old mouse nest. There was a little urine damage on a removable plate shield behind the RF tuner. I removed it and with face mask and ntrile gloves, cleaned off the oxidized cadmium and rust and touched up the affected area of the plate with silver paint. Apart from that and the knawing of the insulation from a wire from the horizontal deflection coils to the horizontal centering pot, the set underneath was pristine. The set did not appear to have been serviced apart from the replacement of two 6SN7s, the 6BG6 and 12AU7. I then put the set away.

After 7 more years of sitting idle, I pulled the set out this week and have finally begun bringing it back to life. I want to follow a restorative process and will not shotgun replacement parts. So I will try not replace anything unless it is proven bad.

Yesterday I first began evaluating the electrolytic capacitors. I use a Sprague Tel Ohmike TO6 Capacitor Analyser which I picked up as trash some 20 years ago. The TO6, besides measuring capacitance and insulation resistance, has a dandy current limited power supply with ammeter for the reforming of electrolytic capacitor dielectric. If you examine the power supply of the attached schematic, you will find that RCA sets of the late 40's used a resistive divider to supply the voltages required in the set. The first thing I do to isolate the capacitors without having to physically remove them, is to lift the top end of the divider chain. This made available five electrolytics on the +225v rail to hook up my TO6 power supply. the negative of the TO6 goes to the -85v rail. The attach points are made readily available when you remove the divider panel as depicted in the photo.

I hooked up the TO6 last night and with 20mA applied, i read an initial voltage of 5volts. Almost a dead short! After about 5 minutes, with current maintained at 20mA, the voltage across the capacitors began to rise. The rule of thumb for reforming is to give 10 minutes plus 1 minute for each month the capacitor has remained dormant. Let's see... that would amount to 10 + (60 x 12) = 730 minutes or about 12 hours. So once I was comfortable that the voltage was rising and the current would not exceed 20mA, I left it cooking for the night.

Next morning, I was pleased to see that the voltage was at 300 but the current was about 10mA, a bit high! the capacitors were across the +225, -85 rails for a total of 310v and the capacitors appeared rated at 350v. So I cranked up the voltage until 350volts to see what would happen. I witnessed a slow and gradual climb and when i was across the room, I shortly heard a pop and what sounded like a pig squeal.

C160, the axial lead 6K6 audio output screen bypass began emitting a little gas and looked as if it was about to give out. I immediately turned off the DC supply and after discharging the capacitors, snipped the lead off the capacitor. In hindsight, I realized that this separately located axial lead capacitor was rated at only 300v and lifting the divider allowed the full 350v across it! No matter as it is easily replaced.

After clipping out the bad C160, I was pleasantly surprised to find the remaining 80, 40,40,30 uF capacitors yield a total leakage of 1.7mA. After another 8 hours at 350volts, the leakage has dropped to 1.5mA. So it looks like the capacitors have been reprieved. On next to the remaining three main electrolytics: C128C Vertical Out cathode bypass, C116A Boost B+, C116B +150v Filter and C128A chassis to -85v filter. The only other two electrolytics are the 1000uF and 250uF low voltage centering pot capacitors which if shorted will only prevent the centering pots from working. i will leave those for later as i suspect if they survived they will reform in normal operation.

More to come.....

Reformed the remaining electrolytic capacitors. I have run the electrolytics at full rated voltage for 24 hours and the leakage current is acceptable. Next to the paper capacitors.

I have lifted one end of three coupling capacitors. The leakage is pretty bad: the video amplifier coupling capacitor was 4 Mohms and will need to be replaced. The audio coupling capacitor is 40 Mohm and I think I will change that. Any capacitor with an appreciable DC voltage across and leakage should go. But there are a number of places where the leakage does not matter and I think I shall weigh on retaining a bunch.

As for the resistors, there is generally a pretty great leeway and even if out of tolerance, unless the resistance is critical, I will likely retain all the resistors.

I'm looking forward to following this.

This morning I began going thru and testing the paper caps. I thought I should test their behavior under DC voltage.

I first examined the 0.01ufd 400v coupling capacitor between the first audio and output stage. I used my old IM18 Heathkit VTVM to initially measure the dielectric resistance. It started slow and climbed to about 40Mohm. A new polypropylene cap would typically climb from near zero to infinity almost instantaneously.

I next applied a 350v DC and monitored current. Interestingly, the initial steady state current was about 1.5mA and slowly began climbing. The current climb began to accelerate and within one minute reached 15mA at which point I cut the voltage. Bear in mind that the 40uF caps reformed and descended to a current of 0.5mA for 24 hours under test.

A similar result with the 0.05uF 400v first to second stage coupling cap. The dielectric resistance was close to 80Mohm yet with 350 volts applied, the leakage current rose from 0.5mA to 4mA within one minute and was continuing to climb when I cut the voltage. I then applied only 20 volts to the third 0.05uF 400v coupling capacitor between the second detector and first video amplifier stage. It generally runs with only about 10volts DC across it. The leakage was under 100uA and did not change. So perhaps not under stress, it can remain.

The paper dielectric capacitors appear to be a serious threat if run with a high potential difference across them. It surprised me that a 0.01uF had considerably more leakage than 40uF electrolytic. Anyhow I shall proceed to change a slew of compromised paper capacitors today.

You'll probably end up replacing the electrolytic capacitors as well, before you are done.

You'll probably end up replacing the electrolytic capacitors as well, before you are done.

Not necessarily. I have four pre-1950 RCA televisions and out of that bunch, there was one electrolytic fail. And it failed by opening and not shorting. I have a CTC5 color RCA with original electrolytics.

Paper dielectric capacitors are a real problem. Good quality Sprague and Mallory electrolytics starting from the late 1940's if properly handled will continue to function today in most cases if the reforming process is done with care. I am highlighting this project because the set sat unpowered for 60 years. If the set had been plugged in, the electrolytics would like have been irreparably damaged.

I spent the day replacing only the paper capacitors I feel would be under stress in circuit positions where subjected to high voltage. The electrolytics reformed nicely with each leaking under 1 mA at rated full voltage.

The paper capacitors, as expected all exhibited various degrees of leakage. my rational in retaining some is if the capacitors have under 1 Megohm in parallel with it. I performed futher tests on the paper capacitors which displayed a worrying thermal runaway failure mode. I placed 350 volts DC across a 0.05 uF 400v capacitor from the set. It showed just over 3mA leakage. However the leakage must have generated internal heat which increased the leakage current. within a minute or so, I witnessed the leakage current begin to accelerate and at 15mA, I removed the voltage. I let the capacitor cool and an hour later i repeated the test with leakage starting at 3mA and rising over time as before. I then reduced the voltage to 20volts and the leakage current was insignificant and remained steady.

I then tested the 0.1 uF 1000v capacitor which is used in the B+ Boost circuit as a filter. At 500VDC, it showed only 0.5mA. However I took a heat gun and raised the temperature of the capacitor only to the point of wax beginning to melt. The leakage increased with the heat. So I ended up replacing all the paper capacitors in the circuits with applied high voltage only except for one: at some point the 6BG6 Horiz Output screen bypass capacitor was replaced with a white bumblebee type. I applied 400v and heated it but the leakage remained at 0.1mA. Do not know what it is composed of or even if it was a paper diectric capacitor. I left it in.

I had a couple of old Black Beauties (0.25uF 400V and 0.1uF 1000V) which I substituted for the wax ones in the set. The Black Beauties under full (or near full in the case of the 1000v unit) showed little or no leakage even when heated.

I replaced the two 0.01uF capacitors from power line to chassis with two Orange Drops rated at 1600v.

I have included a picture of the underside so you may examine for yourself the capacitor replacement work I did today.

POWER UP.

Next came the moment of truth. I inserted the 10BP4, plugged in a cheater and switched it on. I had the chassis on its side to detect any wisps of smoke.

After switching on and waiting about 30 seconds, I heard the vertical sweep start. I advanced the brightness to rotate the ion trap and was rewarded with noise on the screen. I adjusted focus and haven't even touched the Vertical linearity or Vertical Height. I set my Sencore VA62 to and the 721TS to Channel 5 and was rewarded with a picture.

I immediately saw the horizontal hold began to drift and there was a 0.002uF on the Horizontal Frequency Control grid which I was earlier hesitant to replace. I replaced it and the horizontal frequency drift ceased.

Find below a picture of the chassis underside and a picture of the image which immediately popped up. No audio yet and next is the 'soak test to see what will fail. Remember this has been a minimalist rejuvenation and I suspect until a prolonged stress something will fail. Let us see over the coming weeks. More to follow.....

Very interesting experiment! I can't wait to see what happens next.

Found the cause of no audio. RCA in the late 40's inserted a 5.1 ohm resistor in series with the audio discriminator (6AL5) filament. These often go bad. The 5.1 ohm resistor was open in this set and replacing it with two 10 ohm 1 watt metal film resistors in parallel found the audio.

The tuning was off frequency. Touched up channel 13 downward. Replaced the local oscillator 6J6 because ran out of tuning range on channel 13.

Also replaced the 5U4 rectifier. The rest of the tubes are as I found the set.

Total replacement parts count: 11 paper capacitors, 1 electrolytic (the one I inadvertently blew up with over voltage), one resistor and two tubes (5U4 and 6J6). RF/IF alignment still looks good: best point of video matches best audio. 10BP4 is a 1949 spare I had (original was bad). CRT tests low and is a little dim but it works.

Set ran continuously last night for a couple of hours with no major mishap. Will give it 10 hours today to see what happens. I am surprised at this little 73 year old survivor after sitting dormant for roughly 60 years.

The set has been running continuously for 6 hours. Been running a series of DVDs on the set. I have the 1933 film 42nd Street on it now.

Audio was low. I found the 1st audio IF socket dirty. Wiggling the tube in the socket brought the audio level right up. Plenty of audio now.

The picture is good along with good sound.

The electrolytics are fine. They are still cool and the set looks healthy.

Net parts replaced to bring them is set back to life are in the attached photo.

I plan to put a lot of hours on this set this week. Let us see if the electrolytics hold up.

Any idea why RCA put that 5.1 ohm resistor in the filament circuit of the discriminator tube?

Any idea why RCA put that 5.1 ohm resistor in the filament circuit of the discriminator tube?

not a clue, it is also there on the RCA 630ts (which is what my FADA is a clone of ) , but it's
2.2 ohms, and it also feeds the heater of the Horz sinc disc, also a 6AL5

Any idea why RCA put that 5.1 ohm resistor in the filament circuit of the discriminator tube?
Discussion of it here - http://www.foundcollection.com/2_81131c0ab8492ebb_1.htm

Any idea why RCA put that 5.1 ohm resistor in the filament circuit of the discriminator tube?

That is a good question. I thought about this from the different aspects of cathode temperature and space charge or possibly improving discriminator linearity.

I think the clue may be gathered from the Radio Designers Handbook by F. Langford-Smith Fourth Edition (1954) on page 1095 under FM Detectors. RCA was using the Foster-Seeley discriminator which according to Langford-Smith was subject to introducing troublesome heater-cathode hum with a miniature vacuum tube such as the 6AL5. The later Ratio Detector was not subject to the hum problem.

I believe that the introduction of the 5.1 ohms reduced the a.c. heater potential and lifted one leg of the filament from ground to help balance and reduce the hum potential between heater and cathode. Because the 6AL5 is a signal detector in this application, the reduced cathode temperature and resultant space charge reduction would not significantly affect its operation.

This is my opinion and I am open to other thoughts.

The RCA 721 TS ran 10 hours today with no problem. The 10BP4 is dim and has low emission, but produces a reasonable picture.

No sign of any problem with the original electrolytic capacitors since they were reformed. I shall intermittently keep the set on and keep an eye on it.

The 721TS has been running for about an hour this morning. I am told the electrolytics will not last long term. I am curious what evidence is there of that?

There is no sign of any heat or stress on the electrolytic capacitors after running about 14 hours in total. Any thoughts when they will fail?

The point of this exercise is to point out in a project such as this, that perhaps it is unwise to shotgun replace most of the electronic components. I am amazed reading here that even resistors that have marginally drifted out of tolerance are replaced. Paper capacitors indeed go leaky but even then, is it necessary to change all of them even if it makes no difference to circuit performance?

I have previously contested that the wholesale replacement of parts is unnecessary and will likely lead to considerable extra work and grief. It took me less than a day to get this set up and running.

The key here is to scrutinize the circuit in advance to identify components which will likely fail with catastrophic results eg up-in-flames, smoldering resistors or undo stress on the power transformer and rectifier. If concerned, you can always insert a slo=blow fuse in the B+ rail. More time should be spent paning before execution.

I contend the Sprague and Mallory branded electrolytics made from the late 1940's were very well manufactured and will operate satisfactorily and reliably even today. This is if and only if you reform the diectric properly and with a bit of care. In the last 50 years of repairing these old sets, I do not recall ever seeing a bad mica capacitor in an RCA set. I think more time spent understanding how the circuits work will result in less physical effort and result in a set that maintains more of its overall originality.

The 721TS has been running for about an hour this morning. I am told the electrolytics will not last long term. I am curious what evidence is there of that?



If it's going to be a shelf queen and get run for 10 minutes several times a year, you may not have a problem.

I restored a 51 TV earlier this year and did it one part at a time just to bone up on tube troubleshooting. Once done, it was shotgunned (well, not fully done).

This TV has nine electro cans, and two were bad on first power up, one taking out the 5U4, the other taking out a 6X4. I pulled them and restuffed them, and soldiered on.

While working on the sound section, another can that had previously checked fine and had run cool for several hours decided to make itself known. A slight change in the picture followed by a hiss told me another can had enough. Where it was running cool for several hours beforehand, it now was *very* hot. The fact that it was also drooling like a 5 year old kid with a mouth full of Sour Gummy Worms was another clue..

So far, 4 cans restuffed and the other 5 will be done before final assembly. The paper caps that are running fine will also be replaced before final assembly and alignment.

John

You can get lucky and have a set come to life on a minimal recap , and you can get really lucky and have it last, but experience with that approach tells me it's a waste of effort.

I have a 62 Zenith 29JC20 (their first consumer color set) that I tested every lytic for leakage on my Heathkit C3 in and initially changed only 2-4 sections. All the cans ran cool for a few weeks then over the course of a month they started dying at a section or 2 a week after 3-4 rounds of this I got mad and changed the remaining ~3 sections.
My CTC4 also illustrates this... When I got it about 8 years ago I changed all caps, but the doubler lytics (which tested fine and ran cool) ran it for a few months, concluded it had alignment issues and shelves it in a move till covid came knocking... I variaced it and then found changing all the off tolerance resistors fixed the alignment issues I was experiencing. When I finally had it done as I was putting the back on the screen image shrunk and the sides started undulating....you guessed it one of the doublers started leaking.

The minimalist approach is fine for learning, and for sets destined to become low use shelf queens, but daily drivers are too troublesome with original caps...I've learned that the hard way enough to not be convinced otherwise.

If it's going to be a shelf queen and get run for 10 minutes several times a year, you may not have a problem.

I restored a 51 TV earlier this year and did it one part at a time just to bone up on tube troubleshooting. Once done, it was shotgunned (well, not fully done).

This TV has nine electro cans, and two were bad on first power up, one taking out the 5U4, the other taking out a 6X4. I pulled them and restuffed them, and soldiered on.

While working on the sound section, another can that had previously checked fine and had run cool for several hours decided to make itself known. A slight change in the picture followed by a hiss told me another can had enough. Where it was running cool for several hours beforehand, it now was *very* hot. The fact that it was also drooling like a 5 year old kid with a mouth full of Sour Gummy Worms was another clue..

So far, 4 cans restuffed and the other 5 will be done before final assembly. The paper caps that are running fine will also be replaced before final assembly and alignment.

John

I have running four other RCA sets from the late 40's. Two 8T243's (I sold one) an 8TC271 and a 9TC275. The 8T243s and the 9TC271 were dormant and never plugged in and I simply reformed the capacitors and use them regularly with no problem. I have had the 8T243 for 50 years this year (yep I was given it in 1970. I have used it for 50 years since on its original electrolytics. The 9TC275 on the other hand sat in a damp basement and the seller pugged it in until he said he saw smoke. I looked at the electrolytics and two cans were ruined and a third survived. I have a CTC5N color and it has all the original electrolytics. A CTC11 with high hours had bad electrolytics and i ended up replacing them all.

The 721TS I plan to keep and I want to retain as much of t original as possible. And my past reference is more than 50 years of restoring electronic equipment. I see that the Sprague and Mallory capacitors have an unduly bad reputation.

If the electrolytics lasts 100 hours and I do not abuse it I expect it will last the remainder of my lifetime. Would you agree? I would also venture it will outlast a modern replacement if I was to install one.

The 721TS has been running 20 hours now and still running fine...

You can get lucky and have a set come to life on a minimal recap , and you can get really lucky and have it last, but experience with that approach tells me it's a waste of effort.

I have a 62 Zenith 29JC20 (their first consumer color set) that I tested every lytic for leakage on my Heathkit C3 in and initially changed only 2-4 sections. All the cans ran cool for a few weeks then over the course of a month they started dying at a section or 2 a week after 3-4 rounds of this I got mad and changed the remaining ~3 sections.
My CTC4 also illustrates this... When I got it about 8 years ago I changed all caps, but the doubler lytics (which tested fine and ran cool) ran it for a few months, concluded it had alignment issues and shelves it in a move till covid came knocking... I variaced it and then found changing all the off tolerance resistors fixed the alignment issues I was experiencing. When I finally had it done as I was putting the back on the screen image shrunk and the sides started undulating....you guessed it one of the doublers started leaking.

The minimalist approach is fine for learning, and for sets destined to become low use shelf queens, but daily drivers are too troublesome with original caps...I've learned that the hard way enough to not be convinced otherwise.

Miminal recap? I do not think it is as simple as that. It is a process of deciding to replace only what is necessary. There is a 0.25 uF paper capacitor in the cathode circuit of the 6BG6. It bypasses an 82 ohm cathode resistor. Even if the leakage is 5 Megohms, the shunt resistance is a small fraction of the capacitor leakage.

The capacitors I have changed I identified are subject to voltage breakdown. I have only changed the ones I see which pose a threat.

If I experience an alignment problem, I would investigate and if a straight forward voltage check would reveal the restor problem. And yes I would replace them. But I use these sets daily and I have no fear of the component I left remaining breaking down if the set runs on the bench for a couple of days without issue.

I have also seen electolytics fail over time. But did you reform them and check leakage before buttoning on the back cover? I am seeing the average recommended leakage expected on electrolytics of this vintage to keep the dielectric in place. I would have replaced them if the leakage was above my reference limit.

So this set is going to be a daily driver and i will not fear capacitor failure if it gets past 50 hours.

On the a continuing note, I have noticed the 721TS has a slight low frequency smear in the picture. I left one paper capacitor in place in the video amplifier: the 0.05 uF between the video second detector and the input of the first video amplifier stage. The DC voltage across it is only a couple of volts. It may have a high ESR which is affecting the picture. Then again it may be an open peaking coil or a drifted resistor. I put a multiburst from the Sencore VA-62 on the screen and a good clean 3.0 MHz response is seen, which is normal for a 3 stage IF set like this one and the tuning appears correct with no ringing and the video carrier appearing to drop on the nyquist slope and you reach optimum sound.

So the diagnosis continues. And the point of this post is to highlight the process of restoration rather than wholesale rebuilding.

:tongue:

-gets out the popcorn, ready to watch the fireworks! :huge:

You can get lucky and have a set come to life on a minimal recap , and you can get really lucky and have it last, but experience with that approach tells me it's a waste of effort.

I have a 62 Zenith 29JC20 (their first consumer color set) that I tested every lytic for leakage on my Heathkit C3 in and initially changed only 2-4 sections. All the cans ran cool for a few weeks then over the course of a month they started dying at a section or 2 a week after 3-4 rounds of this I got mad and changed the remaining ~3 sections.
My CTC4 also illustrates this... When I got it about 8 years ago I changed all caps, but the doubler lytics (which tested fine and ran cool) ran it for a few months, concluded it had alignment issues and shelves it in a move till covid came knocking... I variaced it and then found changing all the off tolerance resistors fixed the alignment issues I was experiencing. When I finally had it done as I was putting the back on the screen image shrunk and the sides started undulating....you guessed it one of the doublers started leaking.

The minimalist approach is fine for learning, and for sets destined to become low use shelf queens, but daily drivers are too troublesome with original caps...I've learned that the hard way enough to not be convinced otherwise.

Miminal recap? I do not think it is as simple as that. It is replacing only what is necessary. There is a 0.25 uF paper capacitor in the cathode circuit of the 6BG6. It bypasses an 82 ohm cathode resistor. Even if the leakage is 5 Megohms, the shunt resistance is a small fraction of the caacitor leakage.

The capacitors I have changed I identified are subject to voltage breakdown. I have only changed the ones I see which pose a threat.

If I experience an alignment problem, I would investigate and if a straight forward voltage check would reveal the restor problem. And yes I would replace them. But I use these sets daily and I have no fear of the component I left remaining breaking down if the set runs on the bench for a couple of days without issue.

I have also seen electolytics fail over time. But did you reform them and check leakage before buttoning on the back cover? I am seeing the average recommended leakage expected on electrolytics of this vintage to keep the dielectric in place. I would have replaced them if the leakage was above my reference limit.

So this set is going to be a daily driver and i will not fear capacitor failure if it gets past 50 hours.

On the same note There appears to be a slight low frequency smear in the picture. I left one paper capacitor in place in the video amplifier: the 0.05 uF between the video second detector and the input of the first video amplifier stage. The DC voltage across it is only a couple of volts. It may have a high ESR which is affecting the picture. Then again it may be an open peaking coil or a drifted resistor. I put a multiburst from the Sencore VA-62 on the screen and a good clean 3.0 MHz response is seen, which is normal for a 3 stage IF set like this one.

So the diagnosis continues. And the point of this post is to highlight the process of restoration rather than wholesale rebuilding.

Miminal recap? I do not think it is as simple as that. It is a process of deciding to replace only what is necessary. There is a 0.25 uF paper capacitor in the cathode circuit of the 6BG6. It bypasses an 82 ohm cathode resistor. Even if the leakage is 5 Megohms, the shunt resistance is a small fraction of the capacitor leakage.

The capacitors I have changed I identified are subject to voltage breakdown. I have only changed the ones I see which pose a threat.

If I experience an alignment problem, I would investigate and if a straight forward voltage check would reveal the restor problem. And yes I would replace them. But I use these sets daily and I have no fear of the component I left remaining breaking down if the set runs on the bench for a couple of days without issue.

I have also seen electolytics fail over time. But did you reform them and check leakage before buttoning on the back cover? I am seeing the average recommended leakage expected on electrolytics of this vintage to keep the dielectric in place. I would have replaced them if the leakage was above my reference limit.

So this set is going to be a daily driver and i will not fear capacitor failure if it gets past 50 hours.

On the a continuing note, I have noticed the 721TS has a slight low frequency smear in the picture. I left one paper capacitor in place in the video amplifier: the 0.05 uF between the video second detector and the input of the first video amplifier stage. The DC voltage across it is only a couple of volts. It may have a high ESR which is affecting the picture. Then again it may be an open peaking coil or a drifted resistor. I put a multiburst from the Sencore VA-62 on the screen and a good clean 3.0 MHz response is seen, which is normal for a 3 stage IF set like this one and the tuning appears correct with no ringing and the video carrier appearing to drop on the nyquist slope and you reach optimum sound.

So the diagnosis continues. And the point of this post is to highlight the process of restoration rather than wholesale rebuilding.

My Heathkit C3 tests leakage at working voltage. I can also use it to to reform capacitors. I have done a number of sets where any cap that tested as leaking got changed and ones that were good went bad after extend use. Both sets I mentioned went through that and after weeks of use and dozzens of hours of running cool the lytics eventually decided to crap out.

I've found that in the time it takes to evaluate each cap I can recap a set several times over. And the time I waste on repeated repairs on my daily driver sets when I don't do a full recap is worth more to me than the cost of capacitors or maximal originality.

Each part has a bell curve of failure and on high production sets I'm sure some examples may still be usable with all original caps today and into the future...when you find one you are winning the lottery statistically speaking....my luck usually ain't that good and I don't like to gamble my scarse time on unreliable parts after doing similar experiments to yours.

Some makes and models are more picky about exact component value than others. I've seen it for myself plenty, and some who have restored a set like yours and a Muntz will complain that the Muntz will be picky about tubes and precise (not necessarily accurate values but precise) component values.

If the electrolytics lasts 100 hours and I do not abuse it I expect it will last the remainder of my lifetime. Would you agree?

I have no way of knowing how long the caps might last or how often you will run it. It may go 100 hours, it may go 20, or it may go boom the next time you try it...

Anything I restore I do so with the expectation that the next guy won't have a lot to do if something inevitably fails - and that guy will be one of my two sons in most cases.

I have two items of significant age running original capacitors: one of my Fisher X-1000 integrated tube amps from 1962 has all it's original capacitors - my original X-1000 blew a can about 35 years ago. In any case, I don't let either Fisher run unless I'm in the same room with it.

The second is my 1929 RCA Radiola 62. This has no electrolytics at all and the paper capacitors are made with rice paper instead of rag. Radiola experts say don't change any caps in a 20s Radiola unless you run across one.

I would also venture it will outlast a modern replacement if I was to install one.

No chance. Go to DigiKey and order Panasonic low ESR, high pulse caps. These will outlive you and I combined.

The 721TS has been running 20 hours now and still running fine...

I used to do monitor work for an arcade operator many years ago, and he would say that you're on bonus time...

Parting shot: when I restuffed the four cans on my TV, I did a postmortem on the innards and what I found is a lot of degradation in the foil and the paper as I unrolled it. It wasn't a matter of if it was a matter of when. The other five cans in my TV are still original and of the same manufacture, but I know what's inside and I know they need to be serviced before they burn out a part that could only be sourced from the nation of Unobtanium.

John

I've restuffed a lot of late 40's capacitors, about 90% of them are dried up inside with the electrolyte turned to a white crystalline powder and the Aluminum foil is rotted and deteriorated. They often would still work to some extent, but no way were they okay.
Normally they would be damp to actually wet inside.

Low leakage is one part, but have you checked them for capacitance? I suspect the deteriorated ones have lost a lot.

My Heathkit C3 tests leakage at working voltage. I can also use it to to reform capacitors. I have done a number of sets where any cap that tested as leaking got changed and ones that were good went bad after extend use. Both sets I mentioned went through that and after weeks of use and dozzens of hours of running cool the lytics eventually decided to crap out.

I've found that in the time it takes to evaluate each cap I can recap a set several times over. And the time I waste on repeated repairs on my daily driver sets when I don't do a full recap is worth more to me than the cost of capacitors or maximal originality.

Each part has a bell curve of failure and on high production sets I'm sure some examples may still be usable with all original caps today and into the future...when you find one you are winning the lottery statistically speaking....my luck usually ain't that good and I don't like to gamble my scarse time on unreliable parts after doing similar experiments to yours.

Some makes and models are more picky about exact component value than others. I've seen it for myself plenty, and some who have restored a set like yours and a Muntz will complain that the Muntz will be picky about tubes and precise (not necessarily accurate values but precise) component values.

I am not saying I do not replace electrolytics if it is not warranted. When I reform a capacitor, I check the leakage and the final capacitance. If the leakage is low at fill rated voltage and the capacitance is as rated, then I will give it a pass. In this instance I will run the set 100 hours and again measure the capacitance and leakage.

And why do you suggest I am winning the lottery? I have repaired a number of sets and about 25% have retained the electrolytics if they behave. Okay the set remains on the bench for a couple of weeks while I give it a good run though. But I am perplexed why immediately the first thing suggested to do is to replace the electrolytics without even a rudimentary examination?

The set now has completed 25 hours. I am going to investigate the video amplifier this evening and run it a few more hours.

I've restuffed a lot of late 40's capacitors, about 90% of them are dried up inside with the electrolyte turned to a white crystalline powder and the Aluminum foil is rotted and deteriorated. They often would still work to some extent, but no way were they okay.
Normally they would be damp to actually wet inside.

Low leakage is one part, but have you checked them for capacitance? I suspect the deteriorated ones have lost a lot.

oddly enough, the electrolytics on my 1949 FADA tested WAY higher than they were rated for when i replaced them, 2 to 4 times higher, at the time, I had no way to test for leakage, I just assumed they would all be bad, and replaced all caps, paper and electrolytic, most of them, if not all testing much higher than they should.

I've restuffed a lot of late 40's capacitors, about 90% of them are dried up inside with the electrolyte turned to a white crystalline powder and the Aluminum foil is rotted and deteriorated. They often would still work to some extent, but no way were they okay.
Normally they would be damp to actually wet inside.

Low leakage is one part, but have you checked them for capacitance? I suspect the deteriorated ones have lost a lot.

I have measured the capacitance and the capacitance has remained within 20%. Otherwise it would be replaced. Certainly the bad one that fail the reforming process appear deteriorated when opened.

But how do you define rotted aluminum with crystalline powder? I suppose we assume the crystalline is dried electrolyte? There is a chemical process within the can and I would expect the insides to appear messy. What is your evidence it is not supposed to look as it does? Or perhaps the question should be how does it differ from a newer capacitor?

I have also opened 1940's cans to restuff with new caps and found some moist and pliable. Would this mean that the capacitor had remained good? I am defining whether a capacitor is good or fails by capacitance, leakage and life test. Is yours the assumption if the capacitor is more than 30 years old, it must automatically be bad?

oddly enough, the electrolytics on my 1949 FADA tested WAY higher than they were rated for when i replaced them, 2 to 4 times higher, at the time, I had no way to test for leakage, I just assumed they would all be bad, and replaced all caps, paper and electrolytic, most of them, if not all testing much higher than they should.

I have seen this as well. My theory is that before reforming the dielectric, the remaining dielectric is thinner. Hence the capacitance rises. After reforming, the capacitance went down.

I didn't test before reforming in this instance. But after reforming the capacitance was within 20% on the units I tested. (I didn't bother to test ever unit as this would have required additional desoldering-resoldering.

But good observation. And the point I want to make is to try and conserve and maintain as much of the original early electronic circuitry as possible. This can be done with due caution. And remember, if I was doing this for anyone but myself, I would probably resort to changing all the electrolytic capacitors! From a personal side, I like maintaining as much originality as possible.

I have seen this as well. My theory is that before reforming the dielectric, the remaining dielectric is thinner. Hence the capacitance rises. After reforming, the capacitance went down.

I didn't test before reforming in this instance. But after reforming the capacitance was within 20% on the units I tested. (I didn't bother to test ever unit as this would have required additional desoldering-resoldering.

But good observation. And the point I want to make is to try and conserve and maintain as much of the original early electronic circuitry as possible. This can be done with due caution. And remember, if I was doing this for anyone but myself, I would probably resort to changing all the electrolytic capacitors! From a personal side, I like maintaining as much originality as possible.

I did restuff some of the original cans, and when I pulled the guts from them, they were as dry as the Sahara Desert inside...

I did restuff some of the original cans, and when I pulled the guts from them, they were as dry as the Sahara Desert inside...

That is why they are called "Dry Electrolytics"!!! Lol.

That is why they are called "Dry Electrolytics"!!! Lol.

these caps were not the "dry" type.
but became so over time.

"the electrolyte inside the capacitor slowly evaporates away over time,"

https://www.effectrode.com/knowledge-base/echorec-multi-section-electrolytic-capacitor-rebuild/

That is why they are called "Dry Electrolytics"!!! Lol.

Wrong. They're called dry Electrolytics as they are not a can of electrolyte fluid with a thin positive electrode in the center like the set Electrolytics used in 30s early 30s Philco cathedral radios.

If you tear open a good dry Electrolytic of any vintage at the very least there should be some electrolyte moisture on the foil/dielectric roll. If there isn't it's dead or about to be.

That is why they are called "Dry Electrolytics"!!! Lol.

You can understand why I never made it as a stand up comedian. Nobody laughs at my jokes. :dunno:

Well it has another 5 hours which brings it up to a total of 30.

This evening I explored the slight smear. I first discounted RF/IF alignment and checked components is the video amplifier. The peaking coils are all good and the load resistors are within tolerance. I temporarily substituted a new 0.05 uF coupling capacitor between 2nd detector and video amplifier input and no change. I used my trusty grid dip meter to check peaking coil resonance. All appeared normal.

I decided to investigate the IF alignment using the grid dip meter Before even even touching any adjustment, injecting a modulated signal at the mixer in the tuner, I could check the sound trap and visually check the IF in a crude way. The traps were fine and you could listen as the dip matched the sound discriminator "zero" at 21.25 MHz. I did notice the video carrier appeared a tad high on the nyquist slope. It certainly helps to have no AGC as the test was quite simple. Typically for virtually all other sets with AGC, I would put a DC supply on the AGC line to prevent AGC interaction.

I ultimately found the last stagger tuned IF stage tuned to 26 MHz may be pushing up the frequency response around the video carrier. I tried swapping the 6AG5 in the last IF stage with a NOS RCA tube which appeared to reduce the video carrier on the nyquist slope. The multiburst 3.0MHz bar appeared more prominent and when connecting back the DVD player, the picture was noticably sharper.

I have an old but good AVO Mark III transconductance tester and I am inclined to test the 6AG5 tomorrow. I also found that the sync separation is not as good as I would anticipate: at normal contrast, sync separation is fine but the contrast adjustment range is narrow before the picture bends. The 721TS uses the first iteration of the famous RCA 'Synchroguide' circuit but without the sine stabilization. So the performance I see may be normal for this pruned back design. But I will check the 6SN7 and the sync circuitry later tomorrow evening.

Well it has another 5 hours which brings it up to a total of 30.

This evening I explored the slight smear. I first discounted RF/IF alignment and checked components is the video amplifier. The peaking coils are all good and the load resistors are within tolerance. I temporarily substituted a new 0.05 uF coupling capacitor between 2nd detector and video amplifier input and no change. I used my trusty grid dip meter to check peaking coil resonance. All appeared normal.

I decided to investigate the IF alignment using the grid dip meter Before even even touching any adjustment, injecting a modulated signal at the mixer in the tuner, I could check the sound trap and visually check the IF in a crude way. The traps were fine and you could listen as the dip matched the sound discriminator "zero" at 21.25 MHz. I did notice the video carrier appeared a tad high on the nyquist slope. It certainly helps to have no AGC as the test was quite simple. Typically for virtually all other sets with AGC, I would put a DC supply on the AGC line to prevent AGC interaction.

I ultimately found the last stagger tuned IF stage was tuned to 26 MHz. I tried swapping the 6AG5 in the last IF stage with a NOS RCA tube which appeared to reduce the video carrier on the nyquist slope. The multiburst 3.0MHz bar appeared more prominent and when connecting back the DVD player, the picture was noticably sharper.

I have an old but good AVO Mark III transconductance tester and I am inclined to test it tomorrow. I also find that the sync separation is not as good as I would anticipate: a normal contrast it is fine but the range is small before the picture bends. The 721TS uses the first iteration of the famous RCA 'Synchroguide' circuit but without the sine stabilization. So the performance I see may be normal for this pruned back design. But I will check the 6SN7 and the sync circuitry later tomorrow evening.

Here is a shot of the grid dip meter coupled to the tuner mixer tube for the frequency response check. I actually rested the coil on the tube as I swung the calibrated dial. Accuracy is reasonable and the trap null was indicated on the dial at 21.25 MHz. I also see the original green sealing lacquer still on the adjustments which suggests it has never been touched.

Running a so far an hour this morning checking the picture and sound quality. Sound is excellent with no buzz. Picture sharper since the 3rd IF tube change yesterday. Haven't touched the alignment: still has the factory settings.

You can understand why I never made it as a stand up comedian. Nobody laughs at my jokes. :dunno:

Perhaps I should take things less seriously and have a chuckle.

I've been banging my head on the wall with an early tube MPX decoder in a radio that will recognize the 19KHz from a generator but not a station...I have to complete this and some design improvements to the set in a few days. The pressure is making me a bit edgy.

That said your experience leads me to have completely different feelings about vintage capacitors than you, and whats left of my understanding of college engineering reliability statistics tells me I shouldn't change my mind.

.... your experience leads me to have completely different feelings about vintage capacitors than you, and whats left of my understanding of college engineering reliability statistics tells me I shouldn't change my mind.

Well I am a professional Electronics Engineer. I know what I have read and been told. In a professional sense, keeping old capacitors like this is wrong. But heck this is a hobby about extreme vintage televisions. The owners of this set put it away in 1960 and forgot about it because by 1960 it was if not obsolete, quaintly old fashioned and dated.

For historical reasons, I want to keep as much originality to it consistent with it working reasonably reliably. Perhaps even the 60 years it sat unused help preserve the electrolytics? Who knows? All I can say is that the capacitors show the correct leakage and capacity and the set will operate for a dozen hours at a time without getting warm.

As for the other components, so long a the picture and sound remain excellent as the set currently does, what is the issue

From purely a hobby perspective and as I wish to keep this set and because I am technically inclined, I am very happy that I have such a good working set with much of its originality maintained
I am going to keep the set running and will update this column as the set approaches 100 hours on time.

Meanwhile I gave an old 630TS someone tried to repair and gave up on. I am going to give it a go and try to clean up the wiring.

Tis a sad fate indeed suffered by all too many rectifiers .....


I trust my x wife 100 times more than I trust any electrolytic cap that's as old as I am ;)

Tis a sad fate indeed suffered by all too many rectifiers .....


I trust my x wife 100 times more than I trust any electrolytic cap that's as old as I am ;)

The reason you trust your wife more is because you are kinder to her than your electrolytics! If you read earlier thru the thread, the patient and proper reforming of the dielectric is the key. How long running time will it take to convince you the capacitors are okay?

The reason you trust your wife more is because you are kinder to her than your electrolytics! If you read earlier thru the thread, the patient and proper reforming of the dielectric is the key. How long running time will it take to convince you the capacitors are okay?


:thmbsp: I was more or less joking with you , if you noticed I said "my x wife" , no kinder there my friend .

Kinda like your "dry" joke , I guess humor & electrolytics just don't mix :D


;) and yes , I am interested in how long the reformed caps live .

I wish I could find the pictures I have of some old caps I took apart.

When I say rotted I mean exactly that, if you unroll the foil there are areas where the aluminum has been eaten away, with gaps in the foil, there are often lumps from the crystals that have formed that leave dents on the paper insulator, I would guess it's these dents, if they get bad enough, that press through the insulator and cause shorts. I have seen several caps where the connecting leads between the foil and the lugs have corroded completely in two causing an open.

And of course I have opened some 40's caps up to find they are still wet and pristine inside, but that is the exception. I imagine the type of storage and the length of time they have been inactive plays a part.

I'm not trying to be contrary, it's an interesting project to try minimal repairs, but I think it is a gamble that they will continue to work, not a big deal since this is a hobby and if it craps out it's not a big issue.

I'm an amateur hobbyist, so it's usually easier for me to just change them and be done with it rather than wonder if that odd little problem I'm having is being caused by an old capacitor.

I have always been of the impression that electrolytics that are bone dry
cannot out damn bug! OUT! you damn cockroach get out of my keyboard reform.
Reforming is supposed to take solvent.

I have seen caps that were bone dry and had normal capacitance and
took rated voltage, but I assumed that they were that way before going dry.
What think you people.

I hope you fry, damn bug ... wait, no, that might hurt the keyboard. OUT!
Damn coronavirus, keeping the exterminators away!

I have always been of the impression that electrolytics that are bone dry
cannot out damn bug! OUT! you damn cockroach get out of my keyboard reform.
Reforming is supposed to take solvent.

I have seen caps that were bone dry and had normal capacitance and
took rated voltage, but I assumed that they were that way before going dry.
What think you people.

I hope you fry, damn bug ... wait, no, that might hurt the keyboard. OUT!
Damn coronavirus, keeping the exterminators away!

:drunk: Not fair to be drinking and not share with your old TV buddies .....

:drunk: Not fair to be drinking and not share with your old TV buddies .....

Yeah!
https://media.makeameme.org/created/i-like-beer-5bb914.jpg

:beer:

:beerchug:

:drunk:

https://www.youtube.com/results?search_query=i+like+beer

I ran the 721TS another 5 hours today. Ran three movies and film shorts from a TCM DVD.

Electrolytics still fine. Each running cool. Rest of the wax capacitors I chose to reprieve okay. Yesterday when I tested the resistors in the video amplifier, all were within tolerance.

When I obtained this set the width adjustment was set for maximum width. As is, the image on the 10BP4 just fills the mask. Might look around the sweep section to investigate. Certainly the width and height have remained constant over the period of my bench test.

Consider this set sat in a partially insulated attic for over 50 years and the sat in storage for a further seven. I am fortunate it had a quiet existence which may partially explain why much of the original componentry has survived.

Will keep it running to determine if anything will fail. I suppose 35 hours is insufficient to prove that original electrolytics aren't salvageable. So let's give it another 35 hours. I am curious to see myself.

Here are another couple of screenshots from a few minutes ago.

The set has been on for six hours today. Finished off the Judy Garland - Mickey Rooney DVDs. Looking at some late 20's Vitaphone shorts. Here is Blossom Seeley in 1927.

The original electrolytics are still running cool and fine after over 41 hours. Still waiting for them to fail.

Finished off another 8 hours running DVDs on the 721TS now reaching 43 hours since reforming the original electrolytic capacitors. I am impressed with the performance of this set with only 21 tubes. Lots of audio volume, no buzz likely because of its full split sound design. The video is sharp but the resolution above 3MHz is missing since the design has only three IF stages. The lack of any AGC is not a problem with no analog over the air available. Would have been curious how it would have been necessary to adjust the contrast control when switching between local and fringe stations.

I recall using my RCA 8T243 (kcs28 chassis) for analog over the air. This is the set I have kept the longest, having been given it in 1970. (It incidentally still runs on its ordinal elwctrolytics). The high class RCA design for 1948-49 sets feature full 4 MHz resolution, a more sophisticated sync separator and RCA's first television AGC solution using peak sync detection. But most impressive were the dual adjacent channel traps. Despite the wider bandwidth, the adjacent channel rejection was so good, you were able to receive deep fringe signals immediately adjacent to strong local stations. The 721TS had no adjacent channel traps. No problem with a modulator now feeding the set.

But the RCA sets in the late forties were built like tanks. Later design sets, especially with larger screens and with larger deflection angle CRTs put a stress on all of the components which would result in reduced reliability.

So tomorrow we should hopefully be able to reach 50 hours on the original 73 year old electrolytic capacitors.

Cool, I've never even put 50 hours on any of my old sets.

Closest thing would be a cheap 19" RCA from 1970 that I have been using the last couple months to watch old shows on DVD.
Recapped the films but not the Filter, got a dozen or so hours so far but the rejuvenated CRT is likely to die before the caps do.

It is up to 45 hours now. I investigated the picture width problem. I just performed routine voltage measurement and found the horizontal oscillator plate voltage a little low. The 120kohm plate dropping resistor had drifted upward to 150kohm. I replaced it with another 120 kohm 1 watt carbon composition resistor (originality of course) and the width was restored.

I saw the width control adjustment was screwed all the way in to maximum before the set was allegedly retired to the attic 60 years ago. So this must have been an old fault.

I have reverted testing with an older expiring 10BP4 to continue waiting for the anticipated expiry of the electrolytics. I want no more hours than necessary on the CRT.

Somehow I don't think there is going to be a failure. The electrolytics are running cool. And this hasn't been luck or good fortune: my two other pre-1950 RCA tv's have all their original electrolytics and run fine. It is running now and has done another 10 hours continuous running today.

The key is patience reforming the capacitors. That is leaving them attached to a light trickle current 24 hours and slowly reaching the rated maximum voltage. If you do not hurry the process, the capacitors should survive. And I am only speaking for RCA sets: I cannot speak for other manufacturer's sets designed to a budget.

Will aim for 55 hours running time tomorrow.

And I am only speaking for RCA sets: I cannot speak for other manufacturer's sets designed to a budget.



When I started in the TV biz in the early 70s, I replaced many hundreds of can electrics in all brands, RCAs included. Some were from the 50s but most were from the 60s.

Recently, I've restuffed cans that were fine, and every time a little investigation reveals decay in both the foil and the paper. It's actually amazing they work at all at this age.

No amount of reforming will improve the deterioration of the paper or foil or reconstitute dried electrolyte.

John

But the RCA sets in the late forties were built like tanks. Later design sets, especially with larger screens and with larger deflection angle CRTs put a stress on all of the components which would result in reduced reliability.

What are your thoughts on the air core high voltage transformer that RCA started using around 1950? I'm assuming it had something to do with the new wider deflection CRT's, although other manufactures seemed to be using something like a ferrite core flyback transformer with good success. It appears that they used that air core on everything from a 12" to 19" CRT.

When I started in the TV biz in the early 70s, I replaced many hundreds of can electrics in all brands, RCAs included. Some were from the 50s but most were from the 60s.

Recently, I've restuffed cans that were fine, and every time a little investigation reveals decay in both the foil and the paper. It's actually amazing they work at all at this age.

No amount of reforming will improve the deterioration of the paper or foil or reconstitute dried electrolyte.

John Can you quantify the decay you have seen? I mean, what specifically quantifies the intenal degradation of a capacitor that deems it unservicable to you?

Do you replace the resistors and full tube compliment as well, even though they function out of tolerance? The curious thing here is that these reformed old electrolytics after dozens of hours test within original tolerance for leakage and capacity. The vacuum tubes from day one lead a downward spiral and after 13 years of heavy use have degraded.

Is it not of interest that after 43 hours continuous operation the capacitors still run cool and are within the original specifications? This is not loose speculation.

Have you tried to patiently reform the capacitors as I have outlined here? Surely old chassis's are available to try. And if it is your own personal set, what is there to lose? Worried about the power transformer or rectifier? You can always insert a slow blow fuse.

I will reitterate that the capacitors remain healthy after 43 hours continuous operation. How many hours operation will it take to convince?

Can you quantify the decay you have seen? I mean, what specifically quantifies the intenal degradation of a capacitor that deems it unservicable to you?

Yes. The foil as it's unwrapped is generally full of pin holes or outright disintegrates when unwrapped. The paper was mostly just falling apart. How these filters worked at all is amazing.

Do you replace the resistors and full tube compliment as well, even though they function out of tolerance?

No. Resistors, tubes, inductors etc. are different animals.

The curious thing here is that these reformed old electrolytics after dozens of hours test within original tolerance for leakage and capacity.

Which is still higher than a new electrolytic when it comes to leakage readings, and you are talking about a capacitor that is working right now. What happens six months from now?

The vacuum tubes from day one lead a downward spiral and after 13 years of heavy use have degraded.

Tubes wear out faster than other parts yes, which is why they were put in sockets in most cases. But a worn out tube doesn't generally destroy a transformer when it wears out. Sure, certain tube failures cause collateral damage, but even a brand new tube can do that.


Is it not of interest that after 43 hours continuous operation the capacitors still run cool and are within the original specifications?

In the interest of discussion perhaps, but I have no interest in using this single case anecdotal evidence to change what I know as fact.

Have you tried to patiently reform the capacitors as I have outlined here?

Yes. I used to try to save a buck like anyone else. When I first started screwing around with tube radios for my customers in the 80s I would do this. I got tired of seeing the same radio back months or a year later with a bad electrolytic or bad paper cap.

When I restore a radio for a customer, I guarantee it for a full year except for vacuum tubes.


I will reitterate that the capacitors remain healthy after 43 hours continuous operation. How many hours operation will it take to convince?

There is no amount of hours for this one TV that will change my mind on this. The 51 Andrea I'm finishing up has 5 of its original 9 can filters still installed. Two of them let go after dozens of hours of working perfectly.

The other two I restuffed for restoration sake were physically degrading in the manner I described in my first paragraph.

I'm not one to change every part because it's what is expected, I change parts that are either defective or have a history of failing. I have a 1929 Radiola in my living room that is running on all original parts, capacitors included with the exception of 5 of it's globe tubes. The Radiola was built in an era before electrolytics and the capacitors were made with rice paper instead of rag paper. Radiola experts say don't change them unless necessary and indeed, my Radiola has been running 15 years in the time I've had it on original caps.

John

Yes. The foil as it's unwrapped is generally full of pin holes or outright disintegrates when unwrapped. The paper was mostly just falling apart. How these filters worked at all is amazing.

That suggests another study which is to reform an old capacitor and then take it apart to analyse it. I still do not understand your reasoning that if the capacitor fuctio n's within original s specifications how it could function at all with pinholes? How can you be sure that unless you disassemble a new capacitor, it doesn't haved pinholes as well


Which is still higher than a new electrolytic when it comes to leakage readings, and you are talking about a capacitor that is working right now. What happens six months from now?

As pointed out, I have owned an RCA 8T243 from 1949 for 50 years and it retains its original electrolytics. And they remain fine.


In the interest of discussion perhaps, but I have no interest in using this single case anecdotal evidence to change what I know as fact.


Your statement points only to your anecdotal evidence. You are by rote used to changing the capacitors. And as this is supposed to be a hobby dealing with archaic artifacts (ancient TVs) and not with a NASA space project, what is the harm in attempting to retain the set's originality? I am the owner and I will maintain a watchful eye.


Yes. I used to try to save a buck like anyone else. When I first started screwing around with tube radios for my customers in the 80s I would do this. I got tired of seeing the same radio back months or a year later with a bad electrolytic or bad paper cap.

When I restore a radio for a customer, I guarantee it for a full year except for vacuum tubes.


But as I earlier pointed out, this is not for a customer. This is for myself. I would agree with you if the set was out of your control, yes the capacitors should be changed.

And it has nothing to do with saving a few bucks. It is the aspect beyond simply cabinet aesthetics, to retain the historical originality of the set and to make "intelligent" decisions what to retain and to replace. As a professional Electronics Engineer with an MSEE, I precisely know what I am doing.


There is no amount of hours for this one TV that will change my mind on this. The 51 Andrea I'm finishing up has 5 of its original 9 can filters still installed. Two of them let go after dozens of hours of working perfectly.


I cannot comment on the quality of the capacitors used or whether you reformed the capacitors properly. I contend that the capacitors you attempted to use did not reform properly as can be determined by properly applying a stress test of leakage measurement at full rated voltage. If determined that the capacitor is in anyway compromised it must be replaced. In my 721TS case, after reforming, the leakage was well within spec at full rated voltage, which encouraged me to run this test.

Anyhow I shall run the set for another 10 hours today. After it goes beyond 50 hours, I shall test some of the electrolytics and confirm whether or not the capacitors have degraded in capacity or leakage over the 50 hours running time.

But as I earlier pointed out, this is not for a customer. This is for myself. I would agree with you if the set was out of your control, yes the capacitors should be changed.



That's kind of the whole point, isn't it? Your RCA may never have those filters fail and I hope that's what the end result is.

But even when rebuilding something for myself, I do it with the expectation that any future failures will be minor in scope, and it will have a projected life as long or longer than when it was first made. In my store I have my 1936 Philco 60 cathedral that I restored 4 years ago. It's a great conversation piece and so many people are amazed it works. It plays every day from when I get there about 9AM until I close about 4PM. Sometimes I forget to turn it off and it runs overnight or over a weekend. In four years, it only has needed an output tube.

The Andrea 16" TV I'm restoring will go in my front living room with my Radiola and 1850s Smith reed melodeon, and it will be with the expectation that I won't have to repair it except for maybe vacuum tubes at some point. I'll keep my fingers crossed that "hard" parts like the transformers, yoke, CRT etc. will live a long life.

I put the Andrea aside for now as I'm trying to build an exhauster and bellows for the Smith melodeon, but when I get back to restuffing the rest of the cans in the Andrea, I'll take some pictures and post what the cans look like when unrolled.

John

Here's what I found when I unrolled a cap from an RCA 630TS. Rotting aluminum and pinholes through the insulating layer. I've restuffed quite a few and often they look like this or worse.

https://live.staticflickr.com/65535/50044215987_f5204757b3_z.jpg (https://flic.kr/p/2jfeFU8)

Here's what I found when I unrolled a cap from an RCA 630TS. Rotting aluminum and pinholes through the insulating layer. I've restuffed quite a few and often they look like this or worse.

https://live.staticflickr.com/65535/50044215987_f5204757b3_z.jpg (https://flic.kr/p/2jfeFU8)

what cap #is that in the RCA 630TS, if I may ask? :o

Here's what I found when I unrolled a cap from an RCA 630TS. Rotting aluminum and pinholes through the insulating layer.

Interesting and I have seen the same. Notice the foil is very thin and exposing the corroded outer layer you tore the foil.

My question is that if only on the outer exposed foil, the thin aluminum foil has degraded, how about inside? And why how would the minor corrosion materially affect operation if the dielectric maintains low leakage and the capacity remains unaffected?

I disconnected the input filter from the 721TS to measure leakage and capacity this morning. This is after "patient"reforming after the 73 year old capacitor which had not been used for 60 years. The leakage had actually dropped in the 45 hours use from 500uA to 100uA at 400v for the 80uF capacitor. At the high line voltage around here (123vac) the input voltage across this capacitor runs at about 330VDC. The rule of thumb absolute maximum leakage from two sources online suggest 1mA leakage for every 50uf for a 450v capacitor.

One thing I noticed is that the 60 Hz Power Factor is not as good as a new capacitor.

Anyhow here are some meter readings from this morning. The Sprague meter is on the 0.6mA full scale range and reads 0.1mA at the 400v on the VTVM.

Meanwhile try opening up that 630TS capacitor to see if the corrosion permeated the internals. Somehow I don't think it did. Otherwise, the capacitance would have been noticeably reduced.

That suggests another study which is to reform an old capacitor and then take it apart to analyse it. I still do not understand your reasoning that if the capacitor fuctio n's within original s specifications how it could function at all with pinholes? How can you be sure that unless you disassemble a new capacitor, it doesn't haved pinholes as well?


I've disassembled New and old capacitors. New ones do NOT have pinholes or rot like bandersons picture illustrates.

I have seen plenty of old caps like bandersons picture that were rotten inside the foil roll.

Cool, I've never even put 50 hours on any of my old sets.

Closest thing would be a cheap 19" RCA from 1970 that I have been using the last couple months to watch old shows on DVD.
Recapped the films but not the Filter, got a dozen or so hours so far but the rejuvenated CRT is likely to die before the caps do.

Some of my color sets get that much use in a week some weeks. And those sets usually get around that much run time in a month.

My monochrome sets usually see fewer hours.

I have seen plenty of old caps like bandersons picture that were rotten inside the foil roll.

So tell me how that materially affect the operation of the capacitor? I am sure you know if you live in the north, your car can still show rust and still be fully operational.

My point is that you are not scientifically assessing the damage and whether it impairs the operation of the capacitor. I am now inclined to take an old capacitor (I have a parts 630TS with rusty chassis) send it through my reform school, confirm it first measures okay then dismantle it to have a closer examination.

Here's another from the 630TS. Different cap much deeper into the roll.

These caps showed as shorted in my vintage Solar tester.

I routinely test caps before opening them up. Ones that showed shorts or excessive leakage that would not reform often look like this.

I've had many that showed little leakage, but also very little capacitance. Gone open in other words. I see this more often than shorts.

https://live.staticflickr.com/3712/9303830702_383ebfcbe9_z.jpg (https://flic.kr/p/fb9yJb)

Here's another from the 630TS. Different cap much deeper into the roll.

These caps showed as shorted in my vintage Solar tester.

I routinely test caps before opening them up. Ones that showed shorts or excessive leakage that would not reform often look like this.

I've had many that showed little leakage, but also very little capacitance. Gone open in other words. I see this more often than shorts.

https://live.staticflickr.com/3712/9303830702_383ebfcbe9_z.jpg (https://flic.kr/p/fb9yJb)

By the look of it, it seems to be c224 RCA (C5 SAMS) or c220 RCA(c1 SAMS).

Okay, unwrapping a shorted capacitor or one that had failed I would expect the appearance you depicted! My point is if the capacitor reforms with low leakage and an even lower leakage is observed after 100 hours, the capacitor should have no problem in service for 1000 hours.

Again I am inclined to open a good capacitor of this vintage and not one that has failed. The key is that the leakage remains low over time.

And do you honestly intend to run your sets hundreds of hours?

And do you honestly intend to run your sets hundreds of hours?

Some of us do. I have a couple of color sets that I've used 3-50 hours a week every week for 6-8 years.

I really fail to see what the point of all this discussion / contention is all about.
When it has been shown over and over again, (and there are many sites dedicated to this. ) that in the restoration of vintage electronics, decades old capacitors, electrolytic and paper, are inherently unreliable due to entropic degradation, and even though they may seem to work, they are like a time bomb waiting to go off, and best replaced with more modern ones which are smaller, and often will preform better and last longer than what is being replaced, especially if high tolerance long life type is used, and of slightly higher voltage range than the original.
And, as it has been pointed out more than once, these new caps can be stuffed into cans of the old, leaving the visual aesthetics unaffected, or, as in the case of my CTC-16XL, I just unhooked the old caps on the bottom, and placed the new ones various places under the chassis, from the top, you can't tell anything was replaced, and I chose the new caps very carefully, all high tolerance long life, if replacing 80uf @ 450v, I put in a 500v one, 20uf @ 250v = 300v , and so on.

It's MY choice not to risk things on old caps, and I'm sure others feel the same, but if you want to run your stuff with them, go right ahead!:D:yes:

I think the bottom line here is this ;

old capacitors are kinda like old people , some live a perfectly healthy life well into their 90s and some begin to seriously degrade starting in their 60s and don't make 70 . And when those people were young there really was no telling which would see the near century mark VS who'd be worm food by 60 . I'm sure there are those caps that'll live to a ripe old age performing their capacitor duties just fine without missing a beat just as there are plenty of them that are right now going to crap in 5 year old TVs , all the while their antique counterparts are still happily doing the cap thing without a whimper . It's luck of the draw , nothing more , and while I think it's great that those particular caps reformed well and came back to life I don't believe every , or maybe even every other , antique cap can be revived in such manner . As a cool experiment I think it's great that you had success but with the destructive nature of a shorted Ecap in mind I do systematically replace every one in any "daily driver" sets I run , just so that I can feel somewhat comfortable leaving them to run while I do things in other parts of the house without having to keep a literal eye on them ;)

:thmbsp: I , for one , am hoping to see your experiment run well into the hundreds of hours .....

I really fail to see what the point of all this discussion / contention is all about.
When it has been shown over and over again, (and there are many sites dedicated to this. ) that in the restoration of vintage electronics, decades old capacitors, electrolytic and paper, are inherently unreliable due to entropic degradation..


It's MY choice not to risk things on old caps, and I'm sure others feel the same, but if you want to run your stuff with them, go right ahead!:D:yes:

Entropic degradation? I am curious what this is.

I am amused bt your comment "when it is shown over and over again". There is a lot of stuff on the internet by many self proclaimed experts. You have not attempted to test the process and I see you are not willing to accept the evidence I has provided. The set has been on now continuously for over six hours reaching a total of 50 hours and the electrolytic capacitors remain fine.

I am not disputing anyone who chooses to replace the electrolytics. However I am disconcerted by reading here that all capacitors including electrolytic, paper and mica should be blindly replaced.

It is amusing to see defensive reaction to my hobby specific activities. I do not disagree with you if yo prefer to replace the capacitors. I have refilled many electrolytic cans myself, most recently my HP DC power supply. I am only posting this information here to demonstrate to all how the capacitors can survive more than seven decades and still work.

I am going to look inside a reformed good capacitor to see what degradation has occurred. I would also suggest you try reforming an old capacitor properly and then testing it for yourself.

I abhor the practise of applying power or even use of a Variac on a set that has not been thoroughly vetted and corrected. It is fraught with danger and because these electronic devices rely upon oscillators to generated grid bias, will lead to other component failures.

Note in this case, I reformed the capacitors and made all the required component replacements after detailed analysis of the circuit before applying full power. This set came up immediately and worked without issues.

I would also suggest you try reforming an old capacitor properly and then testing it for yourself.



I think you're assuming members of this forum haven't tried this. I won't speak for any other old timer here, but I have tried it as I mentioned in an earlier comment. What I discovered was that it was hit or miss, and therefore a waste of time when your name goes on a repair. Your example, although very interesting, won't change my experiences.

The Andrea I'm working on has a lot more hours than yours (I'd guess it's well over a hundred twenty five hours since February) and 5 of the cans are still good and operating fine, but history tells me that they're on bonus time. Using my own TV as an example, two cans were dead immediately, and two failed some 20-30 plus hours after it was running perfectly. The remaining 5 are still running fine at over a hundred hours. They're still coming out.

Sure, you can have capacitors work after 70 or more years, but proving a capacitor can work at 70 years and proving a capacitor can work for 15 hours a week for the next 10 years is another thing entirely.

I mentioned earlier that I'm restoring an 1850s reed organ melodeon. The leather exhauster is still working, but if don't replace the leather, how long will my wife be able to play the melodeon before the leather tears? 10 hours, 100 hours? Maybe she'll never put enough hours on it, but I'm replacing the leather anyway. Once this melodeon is finished, I don't want to ever take it apart again.

That's the point we're trying to make on this subject.

John

I think you're assuming members of this forum haven't tried this. I won't speak for any other old timer here, but I have tried it as I mentioned in an earlier comment. What I discovered was that it was hit or miss, and therefore a waste of time when your name goes on a repair. Your example, although very interesting, won't sway me at all.

The Andrea I'm working on has a lot more hours than yours (I'd guess it's well over a hundred twenty five hours since February) and 5 of the cans are still good operating fine, but history tells me that they're on bonus time. Using my own TV as an example, two cans were dead immediately, and two failed some 20-30 plus hours after it was running perfectly. The remaining 5 are still running fine at over a hundred hours. They're still coming out.

Sure, you can have capacitors work after 70 or more years, but proving a capacitor can work at 70 years and proving a capacitor can work for 15 hours a week for the next 10 years is another thing entirely.

I mentioned earlier that I'm restoring an 1850s reed organ melodeon. The leather exhauster is still working, but if don't replace the leather, how long will my wife be able to play the melodeon before the leather tears? 10 hours, 100 hours? Maybe she'll never put enough hours on it, but I'm replacing the leather anyway. Once this melodeon is finished, I don't want to ever take it apart again.

That's the point we're trying to make on this subject.

John
+1
I've also reformed and vetted lytics with my Heathkit and watched them fail after dozzens of hours of operation.

I've seen TVs and radios run on original caps and even keep a few that way as shelf queens that rarely get powered. Though even that isn't common since if I power on a display set and it dies on me it could be an embarrassment, and even if it isn't I rather feel confident I can grab anything off my shelf and run it as if I just bought it new without worry.

I put enough hours on my sets to go through certain tubes multiple times. Anything that will help put the next repair farther out into the future and let me tackle repairing something else or let me live my life away from the bench is worth doing.

Sure, you can have capacitors work after 70 or more years, but proving a capacitor can work at 70 years and proving a capacitor can work for 15 hours a week for the next 10 years is another thing entirely.

John

I did mention I have a 1949 RCA 8T243 I acquired in 1970 and still runs on its original electrolytics. If I am fortunate to still be alive in 20 years, I will let you know if the capacitors are still okay.

And I generally do not watch 15 hours of TV. I the 721TS case, I simply left it running while going about other things.

I find it very amusing however how some members of this forum take the subject of electrolytic capacitor replacement so very seriously.

+1
I've also reformed and vetted lytics with my Heathkit and watched them fail after dozzens of hours of operation.


Well I have seen a bunch fail in service. And many have not passed the reforming process and test before putting into service. You have not explained what your criterion is. Instead you trash my observations.

And as as this to me is purely a hobby, if the component fails in service, it provides further enjoyment pulling the thing apart to service it because it is my hobby.

Maybe some of us should stop to reflect and chill out.

I think the bottom line here is this ;

old capacitors are kinda like old people , some live a perfectly healthy life well into their 90s and some begin to seriously degrade starting in their 60s and don't make 70 . And when those people were young there really was no telling which would see the near century mark VS who'd be worm food by 60 . I'm sure there are those caps that'll live to a ripe old age performing their capacitor duties just fine without missing a beat just as there are plenty of them that are right now going to crap in 5 year old TVs , all the while their antique counterparts are still happily doing the cap thing without a whimper . It's luck of the draw , nothing more , and while I think it's great that those particular caps reformed well and came back to life I don't believe every , or maybe even every other , antique cap can be revived in such manner . As a cool experiment I think it's great that you had success but with the destructive nature of a shorted Ecap in mind I do systematically replace every one in any "daily driver" sets I run , just so that I can feel somewhat comfortable leaving them to run while I do things in other parts of the house without having to keep a literal eye on them ;)

:thmbsp: I , for one , am hoping to see your experiment run well into the hundreds of hours .....

Thanks for the comment. I sort of see that as well: some have a grand old age and others sadly die prematurely.

I think the success for a long life, both in human and electrolytic terms is to recognize the symptoms of disease early and address it. Some prefer milder treatment whereas others go for radical treatment. And continuing the comparison no one know absolutely for sure if the remedy will be effective or not.

The set now appears very healthy and runs well after 50 hours in the last four days. No detectable hum, lots of clean audio and a sharp picture on my good 10BP4. And rechecking the leakage on one of the electrolytics,, it has dropped a further 80% in the last 50 hours.

Again this project is to satisfy my own personal interest in preserving as much originality in the 721TS as possible and should in no way dissuade you from replacing vintage electrolytics in your own equipment if you so desire. And if I were to leave the set unattended I would protect it by other means such as a fuse. But I am happy remain with the set while it is on.

I'll easily agree that with better than 50 hours on it and the leakage continuing to drop that those caps have proven themselves at least in the short term . I really am hoping you get 100s of hours out of them because it would further your experiment and show that at least some do survive long term . I saw in your first post that you live in Canada and the set was stored in an attic . I know nothing about the general climate where you live so I'll ask , do attics there get Hell like hot in the summer like they do in the lower States of the US or is the climate cool enough there that the set wasn't subject to regular temperatures over 100 degrees (F) ? If the attic remained cool year round I'd bet that one difference likely made a world of difference in the condition of the caps VS a set stored the same amount of time in a Texas attic .

I actually bought the set in central NY near Schenectady. The was no TV in Canada until 1952 and the first available TV dighna l here was from WBEN TV Buffalo NY in 1948. Muy RCA 8T243 was allegedly the first Canadian built TV manufactured in Montreal Quebec.

I bought the 721TS from the house it was purchased for and sat in for over 65 years. The attic was insulated so I guess it did not get too warm in the summer nor too cold in the winter. The set is interesting as it was quite dirty but typical he chassis was not corroded.

I bought an RCA 8T271 which included survivor electrolytics from a home just outside Philadelphia 7 years ago. The original owner bought the set just after he left the US Army with a bonus and he retained it until his death at the age of 91 in 2013. His family sold it to me and despite it not working and sitting in a corner in ther house for nearly 60 years unused, the electrolytic capacitors all came back fine and are still okay after hundreds of hours. This set, having sat indoors its whole life, had a pristine chassis. It looks like new.

So you have to take each case as it comes, I guess.

The 721TS is currently running and has reached 52 hours. Running some Popeye cartoons.

I grabbed a couple of electrolytics from a rusty old Fada 630TS chassis (cabinet dissolved into shards). Looks like it was stored in a wet shed outside. So the electrolytic will have suffered wide climatic changes.

I started reforming it at 4pm today. It is now 10:30pm and at 450 volts the 10uF and 40uF capacitors in the can connected in parallel show a leakage of 200uA. This shows the capacitor is good. The 40uF measures 45uF and the 10uF measures 15uF.

I have been told I am lucky. Maybe so but I never have won a contest or even a book at the local raffle. So this baffles me why I have so much success and everyone else has horror stories to relate.

With the reformed electrolytic with such low leakage at full capacitor rated voltage, before tearing it apart, I would like to leave it at the full 450 volts for a day to see what happens. I maybe will after over voltage by say 5% to see what happens. Fortunately the failure mode is predictable: when it starts to go, like the paper capacitors, there will be a thermal runaway where the leakage increases creatingvheat which further accelerates the leakage and so on. In a paper capacitor, there is little thermal lag so the paper capacitor thermal runaway is fairly fast. The larger electrolytic thermal runaway is slower and more manageable.

Here is a picture of the reformed 630TS capacitor. Notice the VTVM reads 450 Volts DC and the Sprague TO-6 reads 200uA on the 0.6 mA full scale range. And a picture off the 721TS on the weak 10BP4.

Entropic degradation? I am curious what this is.

I am amused bt your comment "when it is shown over and over again". There is a lot of stuff on the internet by many self proclaimed experts. You have not attempted to test the process and I see you are not willing to accept the evidence I has provided. The set has been on now continuously for over six hours reaching a total of 50 hours and the electrolytic capacitors remain fine.

I am not disputing anyone who chooses to replace the electrolytics. However I am disconcerted by reading here that all capacitors including electrolytic, paper and mica should be blindly replaced.

It is amusing to see defensive reaction to my hobby specific activities. I do not disagree with you if yo prefer to replace the capacitors. I have refilled many electrolytic cans myself, most recently my HP DC power supply. I am only posting this information here to demonstrate to all how the capacitors can survive more than seven decades and still work.

I am going to look inside a reformed good capacitor to see what degradation has occurred. I would also suggest you try reforming an old capacitor properly and then testing it for yourself.

I abhor the practise of applying power or even use of a Variac on a set that has not been thoroughly vetted and corrected. It is fraught with danger and because these electronic devices rely upon oscillators to generated grid bias, will lead to other component failures.

Note in this case, I reformed the capacitors and made all the required component replacements after detailed analysis of the circuit before applying full power. This set came up immediately and worked without issues.


Entropy, a product of the second law of thermodynamics, was the slow, irreversible process of breakdown and decay whereby a complex, organized system inevitably degraded into more chaotic ones.

Well I have seen a bunch fail in service. And many have not passed the reforming process and test before putting into service. You have not explained what your criterion is. Instead you trash my observations.

And as as this to me is purely a hobby, if the component fails in service, it provides further enjoyment pulling the thing apart to service it because it is my hobby.

Maybe some of us should stop to reflect and chill out.
The process is simple: unsolder positive lead(s) of capacitor connect cap to Heathkit C3, check capacitance and if not open check leakage indication on tester at 50V if good select next higher range,if bad wait 2 minutes for signs of improvement if no change in reading or improvement stops change capacitor, if leakage drops to acceptible select higher voltage test range. If a capacitor tests as having acceptible leakage at full working voltage it gets ran in set for several hours and checked for temperature and possibly leakage again later.

Any more than this is well in excess of my patience, and after doing this process for a few years worth of restos I have stopped as I have come to the conclusion that it is a complete waste of my time over changing all capacitors of a type I know are prone to failure....on any chassis mount lytics once the positive is unhooked it is quicker to solder in a new part, the new parts are cheaper than the time I spend on a reforming, and the guarantee that a new production part isn't going to take out unobtainium for better than 25 years is worth more to me than original parts. I'm keeping the original tube circuits in and not shit canning them to install a flat screen and I usually keep the original removed caps in a bag with the set with a copy of the schematic and enough documentation that any future historian could analyze the original design and parts and put it back to stock if they wanted. That is as original as a working set has to be for me.

I agree, Tom.

I don't get why everyone is giving OP so much grief. He's doing an experiment, it seems to be working so far, and if later that turns out not to be the case, well, lesson learned, it's a hobby and he enjoys it so...what's the big deal?

I learned something about what it means to reform electrolytics in this thread.

And I said what I needed to, I will always replace ALL paper and electrolytics in anything 70s and older w/o exception, ceramic disc and mica etc are immune from this.

I'm not trying to give him grief, just replying to comments I agree with or think deserve comment. If he wants to interpret that worse than that is or get defensive that's on him.

I'm sure he likes his process being collectively admonished by most respondents as much as we like him trying to convince us we're doing it wrong...his good experiences directly contradict my experience (and those of other members I'm sure) when I tried the same approach with the same goal years ago (granted for me it was more trying to save scarse money during college than putting maximal originality first).

It's interesting reading about some approaches to reforming for some rare case where it might be preferred, but I won't be convinced my experience of vintage caps failing is wrong.

My method for reforming electrolytics is to use a low current high voltage supply and place a 10K resistor in series with the cap being reformed. I monitor the voltage across the cap which will slowly rise if the cap is a good candidate. I'll monitor the voltage as it rises to the cap's rated voltage then remove and gently discharge the cap and reconnect to the test rig. If the cap is decent it will much more quickly charge to it's rated voltage the second and subsequent times. Interestingly if the process is stopped before the cap reaches it's rated voltage, discharged and reconnected to the rig it will quickly rise to the voltage it got to when it was disconnected and then proceed slowly to it's rated voltage, sort of behaving like a zener diode! I have a 1956 B&W PYE set I've restored and managed to reform all of the multi electrolytic cans. The set has done countless hours with these but it is only used by me. If I was restoring it for someone else I would definitely re stuff the can's. I still have a healthy disrespect of all old electrolytics.

I don't get why everyone is giving OP so much grief. He's doing an experiment, it seems to be working so far, and if later that turns out not to be the case, well, lesson learned, it's a hobby and he enjoys it so...what's the big deal?

I learned something about what it means to reform electrolytics in this thread.

:) Hi Alan ,

;) I am someone , and as such , I am part of the "everyone" who has posted to this thread , and I for one have been totally supportive of his experiment .

As has been well established every case is different with regards to how well the "luck of the draw" has treated old caps and yes there are going to be the ones who reform and live on to perform their cap duties just as there will be ones that will crash & burn as in the photo* I posted in my first post to the thread . I do not believe I was giving him grief when I stated that as a fun experiment sure , I'm right with him and want to see him get 100s of hours out of his reformed caps , but my personal preference especially with daily drivers is to replace all Ecaps as a precursor to the return to daily service .


* I lifted that photo from someone's Ebay listing for an old 1960s guitar amp that was listed as "working perfectly" , and have no relation/involvement in the rectifier flambe depicted there .......

I have been silent the last couple of days. I estimate the set has 75 hours and the electrolytics are fine.

I take exception to the comment Tom made. If the capacitor has sat unused for 60 years, the reforming takes hours. It is an electrolysis process you cannot hurry. In this case the capacitors as would be expected would initially test an almost dead short because in the sixty years the dielectric would have disappeared. That is why even applying a Variac is murdering the capacitors. The key is a gradual process that will take about 24 hours.

I limit the current to no more than 5mA at the start. By the time the 450v was reached, the leakage was about 200uA at full rated voltage. Then test capacity and if it is within 20% of the rated value, it is good to go. The important thing is patience.

So I dug up the crusty old space Fada 630TS clone chassis I had and removed two electrolytics. This set sat in a shed for years and the cabinet was shards. The chassis had a lot of rust and the capacitor were pretty grubby when I removed them. There appears to be a date code which suggest the capacitors were made within a week of each other in August 1947.

I put them onto the Sprague TO-6 capacitor analyser power supply to reform them. After 24 hours each of them reached filled rated voltage with a leakage current for each section below 100uA. And tested capacity and all were within 10%. I have never won a lottery and I do not think this is sheer luck. The success is patience and not using the Variac!!

I am going to punish one of these capacitors by running them at and for good measure 5 to 10% above rated maximum voltage to see if I can get it to fail. The other I will keep it at maximum rated 450 volts and then dissect it. Certainly we should not expect to see a picture similar the Banderson's which was apparently insufficiently reformed before applying normal operating voltages.

Here are the candidates. And remember, this is not one off's or luck. I am finding a consistency here.

My understanding is that the paper insulation is the weak link in saving these. Once that insulation deteriorates allowing adjacent foil layers to touch, I don't believe any level of reforming will assure a new anodized dialectic to form on the foil in those areas. I'm assuming the paper insulator material deteriorates because of contamination and exposure to atmosphere rather than improper re-forming practices(as witnessed with paper coupling caps). As far as keeping old electros healthy, I'm inclined to believe that the survivors were more likely used more often and to a later date than those that didn't make it, which likely helped maintain their dialectic layer on the aluminum foil. :thmbsp:

Anybody here have electrolytic caps that are >3 years old that are failing? I have a few recapped radios that started randomly humming, I'm gonna check those 'lytics tonight when I get home......

I have been silent the last couple of days. I estimate the set has 75 hours and the electrolytics are fine.

I take exception to the comment Tom made. If the capacitor has sat unused for 60 years, the reforming takes hours. It is an electrolysis process you cannot hurry. In this case the capacitors as would be expected would initially test an almost dead short because in the sixty years the dielectric would have disappeared. That is why even applying a Variac is murdering the capacitors. The key is a gradual process that will take about 24 hours.

I limit the current to no more than 5mA at the start. By the time the 450v was reached, the leakage was about 200uA at full rated voltage. Then test capacity and if it is within 20% of the rated value, it is good to go. The important thing is patience.

So I dug up the crusty old space Fada 630TS clone chassis I had and removed two electrolytics. This set sat in a shed for years and the cabinet was shards. The chassis had a lot of rust and the capacitor were pretty grubby when I removed them. There appears to be a date code which suggest the capacitors were made within a week of each other in August 1947.

I put them onto the Sprague TO-6 capacitor analyser power supply to reform them. After 24 hours each of them reached filled rated voltage with a leakage current for each section below 100uA. And tested capacity and all were within 10%. I have never won a lottery and I do not think this is sheer luck. The success is patience and not using the Variac!!

I am going to punish one of these capacitors by running them at and for good measure 5 to 10% above rated maximum voltage to see if I can get it to fail. The other I will keep it at maximum rated 450 volts and then dissect it. Certainly we should not expect to see a picture similar the Banderson's which was apparently insufficiently reformed before applying normal operating voltages.

Here are the candidates. And remember, this is not one off's or luck. I am finding a consistency here.

The ones that the leakage didn't drop fast on got replaced with new capacitors... meaning some potentially reformable caps got changed.... despite that the best of the original caps still eventually failed. If the ones that don't have measurable leakage on my C3 from the beginning are going bad then the ones that were leaking sure as hell are not going to last.

Anybody here have electrolytic caps that are >3 years old that are failing? I have a few recapped radios that started randomly humming, I'm gonna check those 'lytics tonight when I get home......

My Philco 60 started hummng 3 years after a total rebuild. Bad output tube..

John

If the ones that don't have measurable leakage on my C3 from the beginning are going bad then the ones that were leaking sure as hell are not going to last.

Back when I became a full time bench tech (70s), I was changing can caps almost daily, and these coming from TVs with a quarter of the years on them that we have now and despite having a fully formed oxide layer from daily use...

Every parts store back then had a full line of Cornell-Dubilier, Arcolytic, Mallory, or Sprague drop in cans.

NOS, used stock, reformed.. they're all time bombs - even back then when they were only a few years old. It's not a matter of if it's a matter of when.

John

The 721TS had only another 7 hours this past couple of days reaching about 80 hours. No sign of the capacitors failing.

Have been running one of the 630TS capacitors I had reformed at its full rated 450 volt rating. Will leave this for a week and monitor the leakage current.

One consideration: the late 40's RCA sets had full wave power supplies with capacitor of relatively low capacitance e.g. 40uF to 80uF at 450v. There are a number of factors in the design that put less stress on the electrolytics in these early sets: ripple current in the full wave rectifier, low deflection angle tubes which required less defection power etc. In the fifties, the designs pushed the limits of components to keep the consumer purchase cost down. The electrolytics were stressed with higher ripple currents, increased capacity in the same form factor. I know the RCA CTC11 color set I have has had to have all its electrolytics changed. The voltage doubler capacitors have been changed twice!

So there are various factors at play here. There is no one size fits all solution and I am only citing the specific capacitors used by RCA in their sets in the late 40's in this instance.

As this is a hobby endeavor and I am speaking from a hobbiest point of view with regards to conservation as opposed to wholesale rebuilding, intelligent assessment of the components is advised. The 1949 RCA 8T243 television which I am still running on its original capacitors I have owned for 50 years and the set still performs fine.

I have been servicing radios, TV sets, and hi-fi/theatre/jukebox amps for 50+ years now; the problems with electrolytic capacitors were well known, even back then. Today, that stuff is 50-90 years old, and those old caps are like a time bomb. The survival of a "dry" electrolytic capacitor is largely due to the integrity of the rubber seals on the case. Once the electrolyte dries up and corrosion sets in, it's dead.

When servicing for a customer or commercial account, reliability is of the utmost importance, to avoid the dreaded "callback". Hobby work is different, of course, but when a reformed capacitor fails anyway and has to be replaced, it's time wasted.

Except for commercial theatre-sound and jukebox amplifiers, most consumer equipment back then did not have an AC fuse, and a shorted capacitor can take out the power transformer. New capacitors are cheap insurance, and I add a fuse in the AC line for more protection.

And update on the 721TS running its original capacitors. It has now reached 350 hours. I am writing today because I pulled the chassis to make a minor mode e.g. reduce the value slightly of output transformer primary parallel capacitor at the plate of the 6K6. This is provide the audio with a bit of a treble boost. I find they liked muddy audio in the '40's.

I looked at all the original electrolytics and they are remaining cool. I disconnected two to measure leakage and they are well below 1mA.

I haven't spent much time on the two electrolytics I pulled from a junked 630TS chassis. I had been running these capacitors rated a 450v on a 450 volt supply. I left them 48 hours and the leakage remained about 0.2mA. I had put them aside the last few months and will continue my test on them. Ultimately I planned to tear them apart to look inside but they have held up well.

I think the key is the patient reforming. Never run even a variac to a set 70 years old until reforming the capacitors. While reforming, monitor and limit the current to no more that 10mA at the start and monitor regularly as the dielectric reforms. At the start of the reforming process on the 721TS, the voltage remained at about 10 volts at 10mA for about 10 minutes until it started to climb. In about 6 hours the current at 400 volts was about 1.5 mA and leaving it overnight brought it down to less than 0.5 mA. Testing today the couple I tested the leakage remains the same.

The key is patience. My background is electronics engineering and I have been repairing vintage electronics since the late '60s. In the last 50 years, I have done my share of electrolytic replacements. I am only pointing out that I do not immediately condemn the capacitor until I test it out. I recently restored a 1954 HP High Voltage 0-600 volt Regulated DC power supply and found four of what I would have expected to be quality capacitors bad and had to restuff them. So I insist this doesn't always work. But if good quality Sprague or Mallory electrolytics are used, it is worth giving them a chance.

I have an 721TS update. It's not about the filter capacitors this time. The set has about 350 hours since my minimalist restoration and the filter capacitors are still fine).

This is about a nagging sync problem. I am surprised how well this little set works despite it being a pared down design. The sync separator is very basic: a sync amplifier fed from the video amplifier (12AU7) plate to a 1/2 6SN7 Sync Amplifier followed by a 6AL5 sync clamp to1/2 6SN7 sync separator. The set is pre-AGC with the contrast adjustment controlling gain in the RF/IF section of the receiver.

The problem stems from a relatively narrow adjustment range affecting horizontal sync. This set features the earliest version of RCA's classic a later widely licenced Synchroguide Horizontal AFC without the stabilization coil. I checked pin 6 (cathode follower sync feed) as I varied the contrast control and found that the sync separation diminished either side or a very narrow range of contrast adjustment. In other words, the sync separation was not very good.

This is not suprising considering the limting factor of cost in the design. The sync clamp or limiter works well as it keeps the sync tip at at fixed DC level. I tested and swapped the 6SN7 with no improvement. And the capacitors all tested good resistor values good.

I was tempted to swap the low amplification factor (20) 6SN7 with a (70) 6SL7. But this would require further redesign as the amplifier gain would be too great.

Picture 1 is the Sync Section of the 721TS with the modification applied.
Picture 2 Is the 621TS Sync Separator included for comparison.
Picture 3 is the separated horizontal sync.
Picture 4 is a picture off air of TVO this evening via an RCA branded set top box. The set is running behind where I am writing this.

I ultimately considered altering the cut off of the sync separator portion of the 6SN7: by applying a pull up resistor of 510kohm as depicted, the clipping action would remain wider with video gain changes. The result is that the waveform depicted was maintained at a somewhat wider range of contrast adjustment. This will be displayed in the video as less video pulling of the horizontal sweep as the contrast control is adjusted.

The sync separator cathode after adding the resistor, showed less ingress of video (in the range depicted with the white arrow) over a wider range of contrast control adjustment.

I would be curious how other with the 721TS finds this problem with contrast adjustment. I have included the circuit of the 621TS which is very similar to the overall design to the 721TS. The 621TS uses the earlier 6H6 as opposed to the 6AL5 for the sync clamp. And the 621TS is still pre-Synchroguide and would be curious how the contrast adjustment affects it.

I have added the resistor and am happy with the overall result.

Below:
Picture 1 is the 721TS sync separator diagram with the modification made.
Picture 2 is the 621TS sync separator included for comparison.
Picture 3 is the 721TS sync separator output horizontal sync waveform with the range depicted where you will see video ingress when the contrast control is adjusted.
Picture 4 is the set sitting behind me as I write. It is receiving this evening TVO (TV Ontario) via an RCA Branded set top box.

II know I am winding everyone up by posting this. But the set has I expect past 400 hours. In my pandemic office at home where I work, I have been runni g the set about six hours a day. CHCH-TV runs old sixties,/ seventies shows all day.

I had the set apart at about 350 hours to check the electrolytics. The two I tested (rectifier output) leakage was about 400uA at full rated voltage which is normal.

The only electrolytic which was bad was a tubular axial mount 25uF at the audio output supply. This,was replaced as it failed my original test. All others have remained original. And about half of the original paper capacitors I left if they were in the circuit shunted by a resistance of 100k ohm or lower. All the other paper capacitors have been changed.

A couple of resistors,were changed as they were out of tolerance and affected performance.

Here,are so.e snapshots from this afternoon oat via an RCA ATSC set top box.

I work from home these days. I switch on the set and tune it daily to an OTA station via my little RCA STB to a local channel that runs 60's -70's shows. It is on about four hours most weekdays. I run it for a few hours on the weekend as well. Still running on the original "properly reformed" electrolytics. Must be in the region of 700 hours now.

This set is a good little performer. A problem occurred a few weeks back when the video went away. Traced it to the last video IF plate load resistor opened.

Recall this was a set I only changed the paper capacitors that I deemed stressed. That is with a high DC voltage across. I left a bunch of original capacitors used for bypass that have only a few volts across. I also left the vertical integrator caps. One electrolytic did not reform: it was the radial lead electrolytic bypass to the audio output screen grid. It had to be replaced all other electrolytics reformed to low leakage at full rated voltage, so I left them to see how long they would last.

Two resistors have been replaced: the aforementioned last IF plate load and the plate supply dropper to the Horizontal Oscillator.

Needed to touch up the video IF alignment after the IF load resistor replacement. Did it by eye by checking to see the carrier is at 50% by taking note of the brightness and the detail and rocking the fine tuning back and forth. A half turn of the last IF coil slug did the trick. Helps that it does not have AGC.

Well, kudos to whatever electrolytics RCA used. Personally, I just want my sets to run reliably, so I just replace the electrolytics seeing as though they may not be whatever brand/spec that RCA used. Not all electrolytics are this marvelous.

It seems like during the course of this you have had a number of resistors fail. Maybe I should be replacing all the resistors for reliability, LOL.

Curious I found RCA electrolytics have been vey reliable. I had a 1949 9TC275 set with a slew of bad electrolytics it was stored in a wet basement in Chicago which may account for it. I have four other late '40's RCAs and all have original electrolytics. As I pointed out, the slow reforming did the trick: limiting the maximum current during reforming to no more than 10mA. And never applying power to the set until it has first been thoroughly vetted. Variacs and direct power application after sitting dormant for 50 years is a sure killer.

As for overall reliability over the last 6 months, the little 721TS has only had the one resistor failure in service. It just suddenly opened up.

The 1947 RCA 721TS is still chugging along on it's original electrolytics. As I pointed out earlier, if the capacitor dielectrics are slowly and carefully reformed and the capacitors are afterward tested to confirm low leakage, they will last and last. This set had sat dormant for nearly 60 years in a house near Schenectady NY. So it must have been purchased to receive WRGB in those days.

It must be well over a thousand hours since I did the minimal rrevival, replacing only the paper capacitors which would likely fail. I left in the paper capacitors which are shunted by resistances 1Meg ohm or less.

The set is frequently run the set for hours at a time. had it on this evening when I recalled this thread.

I will check in the next year or so with another update.

I don't know how I've missed this thread this long. It's been a good read though.

My 1954 Crosley is running on the original electrolytic cans. I tested them in 2006 and they all sections checked out fine so I never bothered to change them. I have no idea how many hours I have on that set, but it was used daily fom fall of 2006 to around 2011 and less frequently after that, and have had no issues with the electrolytic can. I tested it in the winter of 2015 while I had the chassis out working on a intermittent lose of horizontal oscillation and it still tested out fine. It's also running on the original selenium rectifiers too.

I don't know how I've missed this thread this long. It's been a good read though.

My 1954 Crosley is running on the original electrolytic cans. I tested them in 2006 and they all sections checked out fine so I never bothered to change them. I have no idea how many hours I have on that set, but it was used daily fom fall of 2006 to around 2011 and less frequently after that, and have had no issues with the electrolytic can. I tested it in the winter of 2015 while I had the chassis out working on a intermittent lose of horizontal oscillation and it still tested out fine. It's also running on the original selenium rectifiers too.

The electrolytics in your TV are nothing short of amazing, if they have lasted 67 years and are still going strong -- especially if the set was used daily from 2006 to 2011. In most TVs, these capacitors would have failed (shorted, leaky, etc.) by now. What is the secret, if any, to your set's original electrolytics having lasted this long?

That your TV itself is still working is amazing as well, especially after 67 years. Are you using this set as a video monitor for games, a computer, etc., or, if you are still watching TV with it, are you using a DTV converter or a cable box?

It may appear unusual that the Crosley or RCA electrolytics have survived 70 years. I think it should be less surprising if the electrolytics are made by Sprague or Mallory.

The electrolytics in your TV are nothing short of amazing, if they have lasted 67 years and are still going strong -- especially if the set was used daily from 2006 to 2011. In most TVs, these capacitors would have failed (shorted, leaky, etc.) by now. What is the secret, if any, to your set's original electrolytics having lasted this long?

That your TV itself is still working is amazing as well, especially after 67 years. Are you using this set as a video monitor for games, a computer, etc., or, if you are still watching TV with it, are you using a DTV converter or a cable box?

I used to use it for OTA TV back when analog was still on, then I switched over to just the VCR and DVD. I don't know what the secret is, I just let them charge on a capactor tester and bump the voltage up when they test no leakage at that voltage.


Most of my test equipment is running the original electrlytic cans as well and it's all 1950's early 60's gear.
The newest gear on my bench is a B&K Television Analyst 1076.

Sets I've pulled out of damp garages and basements seem to be the ones that have bad electolytic cans. They'll start gassing around the terminal pins. I guess the moisture gets in there with time.

Wrong message, how to delete this message?

Well it is over a thousand hours now. I have the set in my work office and leave it running through the day. The electrolytics show no sign of failing.

The KRK2 tuner has however a problem with the fine tuning capacitor. The rotating capacitor shaft is loose making it awkward yo find tune. Purely a mechanical problem I will investigate next week.

Well it is over a thousand hours now. I have the set in my work office and leave it running through the day. The electrolytics show no sign of failing.

The KRK2 tuner has however a problem with the fine tuning capacitor. The rotating capacitor shaft is loose making it awkward yo find tune. Purely a mechanical problem I will investigate next week.

How are the CRT and receiving tubes faring after 1000 hours? Just putting this into perspective, we've put 1000 hours on a riding lawnmower over a period of 8 years and consider that it's fully depreciated. Likewise it's a remarkable amount of TV time and quite a testament to late 40's electronic technology. In so many ways this has been one remarkable TV. :yes: :thmbsp:

How are the CRT and receiving tubes faring after 1000 hours? Just putting this into perspective, we've put 1000 hours on a riding lawnmower over a period of 8 years and consider that it's fully depreciated. Likewise it's a remarkable amount of TV time and quite a testament to late 40's electronic technology. In so many ways this has been one remarkable TV. :yes: :thmbsp:

That is a good question. I tested the tubes on my AVO MkIII tranconductance tester when I was resusitating this set. The set has required a touch up of vertical height and linearity. Curiously I had to reduce width slightly. As far as RF sensitivity or the quality of video and audio, no noticeable degradation.

A few carbon resistors discovered drifted when initial restoration and troubleshooting were replaced. I only tested and changed resistors which obviously would affect performance. An example was insufficient horizontal drive due to the oscillator plate supply resistor drifting upward. I intentionally replaced the resistors with period new old stock carbon resistors.

Recall I only changed the paper capacitors for which leakage would cause bias problems. That is if leakage was acceptable in the circuit, I left it in. That accounts for about a quarter of the original paper caps remaining. All of the original electrolytic chassis mounted cans after 1000 hours remain healthy which is remarkable after 75 years.

The CRT was a late 50's replacement shortly before the set was put into storage and so the emission remains good. Typical of late 40's CRTs, the focus isn't perfect across the entire CRT but the set does provide a decent picture.

In summary, I think the greatest concern for reliability back then and now is the paper capacitors. In order to make a reliable yet as original as possible set, a lot of thought was given to the restoration strategy. This included understanding how the circuits functioned and anticipating problems. Certainly during the initial extensive bench test monitoring a close eye was kept on the original electrolytics for failure. After 1000 hours they are still fine.

It is a daily runner: I had the set on today for about 5 hours. It will probably be on for about 10 hours this weekend.

The RCA 721TS has been running continuously for 10 hours today. I switched it on at 8:30am and it is now past 6:30pm. It keeps me company while I work at home.

It is still running on it's original electrolytics and I am still waiting for them to fail after 1000 hrs plus.

Last night an electrolytic died in my RCA CTC-5 Whitby shortly after switching it on. I had reformed all the electrolytics and replaced all the paper capacitors when i restored the set in 2012.

The capacitor that died was a Canadian made Mallory on the 25Hz subchassis! The additional subchassis weighs about 35 lbs And contains a massive B supply power transformer, choke and two 80ufd 450v capacitors. The additional filtering was to help minimize the 25 Hz ripple.

The set itself was manufactured in Camden NJ and must have gone by Montreal for the modification. I found that the modification was not well done initially: I found the power lead to the chassis interlock socket was never soldered. It had been like that for over 55 years and there was signs of arcing. Amazing as it must have been bothersome although the set had low hours and I expect the original owners gave up on it.

The Camden capacitors are all Sprague and were very healthy when reformed: the leakage after careful reforming was below 100 uA at full rated voltage. The Mallories were much more leaky at about 1 mA at full voltage. I was tempted to replace them in 2012 but as they did not get warm in operation, I decided to give them a chance. The set subsequently has had a fair bit of use over the last 9 years so I won't complain.

The short took out one of the 5U4 rectifiers and a 15 amp household fuse and nothing else. As you can see the auxillary B supply and the replacement chassis mounted filament transformers are massive and escaped unscathed.

From the photo, the replacement capacitor is in the short can (the old can cut open and restuffed) and it's original companio for testing. After running the set for an hour, it is fine. However I think I will restuff the other Mallory as I have now no trust in it and it may fail in the next 5 to 10 years.

The 1947 RCA 721 TS is still soldiering on with it's original chassis mount electrolytics. It is coming up to a year and 7 months since my minimal rehabilitation. The axial lead 20ufd electrolytic used for audio output plate and screen bypassing was replaced as it failed my leakage test after reforming. To remind all, two resistors, three tubes, fourteen paper capacitors. Recall I left some of the paper capacitors in if they did not upset any DC levels.

I expect it has close to 1400 hours now.

CHCH TV channel 11 went on air in 1954 and their daytime peogramming in HD are retro programs from the 50's thru the 70's. Oddly, the stations do not multiplex up here probably due to the Canadian media monopoly which favors cable and satellite over terrestrial television. Even the CBC tried to abandon terrestrial TV but failed and only run minimal services over the air.

Anyhow CHCH which appears to be about the last independent terrestrial broadcaster in Canada uses the original 1950's logo mascot. I captured a snapshot off air on the 721TS a few minutes ago with a snapshot from the web.

That is pretty cool to have that old station broadcasting vintage shows. Are you feeding the TV with luma only from a converter box?

That is pretty cool to have that old station broadcasting vintage shows. Are you feeding the TV with luma only from a converter box?

No the box unfortunately has composite video out. Even though this was a cheaper line RCA set with only three video IF stages, you can still make out the color dots on saturated colors.

The tubes are doing well. I never actually tested them but I see no appreciable aging. The CRT was a replacement CBS Hytron from around 1957 and has low hours. I bought the set from just outside Schenectady (it must have received first WRGB which claims to be the oldest TV station in the U.S.) from the original owners. I mentioned earlier in this thread how the family retired the set to the attic around 1960 where it sat for 55 years. It was in remarkably good shape apart the laquer finish flaking and from mice nesting under the chassis. (When I pulled the chassis, it was filled with cotten. Only the focus wire was partially nibbled). Most of the tubes are original RCA and so this set must have had a fairly light life.

I have four TVs using this chassis I haven't gotten to restore. a 721 I just picked up, two 8T241s and a 9T240.

This thread is encouraging because I dread replacing the dozen or more electro's these particular RCAs use.

Among my 21" sets, whatever Zenith used in '66 and 67' had reformed well.
BUT the two CTC-11's, 12's, 16x and 20c ALL needed the electrolytics replaced just to get rid of all the lingering issues caused.

I suspect the common ground fails and other things happen to these cans, creating high impedance connections internally due to corrosion from humidity, freezing and other factors.

.

Among my 21" sets, whatever Zenith used in '66 and 67' had reformed well.
BUT the two CTC-11's, 12's, 16x and 20c ALL needed the electrolytics replaced just to get rid of all the lingering issues caused.

I suspect the common ground fails and other things happen to these cans, creating high impedance connections internally due to corrosion from humidity, freezing and other factors.

Interesting as I have found similar. Mt RCA CTC-11 all of the original electrolytics were bad and had to be replaced. I replaced all apart from one supplying the B+ to the Vertical output and after a month it failed. The failure mode was opening up rather than shorting.

I have besides the 721TCS, an 8T243, 8TC271 and 9TC275. Each of the chassis mount capacitors reformed okay except for the 9TC275 under chassis mount capacitor. And my CTC5 had one electrolytic fail at turn on. But is was on the 25Hz subchassis added by RCA Montreal. The Camden mounted capacitors were excellent. (I suspected the Canadian electrolytics would fail as the leakage approached 1mA after reforming at full rated voltage whereas the Camden capacitors were at or under 100uA.

I think the takeaway here is after reforming, testing at full rated voltage or 10 % above, leaving it connected for aat least 30 minutes at this state (to check for thermal runaway) and ensuring the leakage remains no higher than 200uA. And of course after this it retains it's specified capacitance. If it can survive this punishment, then it will be okay in service.

The 1947 RCA 721 TS is still soldiering on with it's original chassis mount electrolytics. It is coming up to a year and 7 months since my minimal rehabilitation. The axial lead 20ufd electrolytic used for audio output plate and screen bypassing was replaced as it failed my leakage test after reforming. To remind all, two resistors, three tubes, fourteen paper capacitors. Recall I left some of the paper capacitors in if they did not upset any DC levels.

I expect it has close to 1400 hours now.

CHCH TV channel 11 went on air in 1954 and their daytime peogramming in HD are retro programs from the 50's thru the 70's. Oddly, the stations do not multiplex up here probably due to the Canadian media monopoly which favors cable and satellite over terrestrial television. Even the CBC tried to abandon terrestrial TV but failed and only run minimal services over the air.

Anyhow CHCH which appears to be about the last independent terrestrial broadcaster in Canada uses the original 1950's logo mascot. I captured a snapshot off air on the 721TS a few minutes ago with a snapshot from the web.

Do you get any American TV stations OTA (or are such stations available on cable) where you are, or is it all Canadian? I would think you would get a few American stations there, as most American cities close to Canada will receive at least one U.S. station (for example, in Detroit, Michigan, viewers can get CBET-TV channel 9, formerly CKLW-TV). I mention CBET because it can be received in my area near Cleveland, when the atmospheric conditions are right; the station is also available in Detroit, which has channels 2 (Fox, formerly CBS), 4 (NBC), 7 (ABC), 50, 56 and 62 (the last being CBS; this station took the CBS affiliation from channel 2 some time ago, in the same manner as CBS-TV in Cleveland was moved from channel 8 to channel 19 (!) in the late 1980s; this was a very stupid move, in my opinion, since channel 19 is a UHF station which is not received well in some parts of northeastern Ohio unless you have cable, satellite or YouTube TV).

In the analog tv days, it was relatively easy to receive OTA from Buffalo NY from the Toronto area. I am to the west of Toronto on the Niagara escarpment and from here you could receive Buffalo NY, Erie PA and Cleveland OH. witha 50 foot tower and a good antenna.

Those were the VHF days. Now that most of the stations have moved to UHF, reception is more difficult. But can still pick up a few US stations but not as before.

It is frustrating because the Canadian media monopolies of Rogers-Bell-Shaw have no interest in OTA television as their primary interest is the ever diminishing revenue from their cable and satellite monopolies.

I was taught Canada was part of the American continents, so technically Canadian broadcasts are American too, no?

No.

I guess that just goes to show how history is changing, and I'm Old :D

I guess that just goes to show how history is changing, and I'm Old :D

Technically Canada broadcasts in North America making their transmissions a North American broadsact. So Titan1 must think the USA is in South America...

I think what was being meant by the comment is that Canadian broadcasts and US Broadcasts while they are North American broadcasts, Canadian Broadcasts aren't "American" Broadcasts, as in USA broadcasts, (when one uses the word "American" generically like like what Kevin did in his post, you're not specifying which part of North America, because US broadcasts would be referred to as "American Broadcasts" whereas broadcasts in Canada would be referred to as "Canadian Broadcasts".

That's why you shouldn't use such broad sweeping terms when talking about something like that, because you can easily misidentify things (or countries or broadcast standards) by using such generic terminology like that.

What should of been said was: "Aren't Canadian broadcasts technically "North American Broadcasts"? rather than "Aren't Canadian broadcasts technically "American Broadcasts"?

It removes any ambiguity that could be there, especially when you have a country like the US that has the word "America" in its name ("United States of America") and the occupants of said country are called "Americans", and anything associated with said country is called "American", including its television broadcasts.

I hope that explanation was helpful.

The set and it's electrolytic capacitors are celebrating their 75th anniversary this year. This past week I sadly had to restuff the last wet electrolytic in my 1935 Scott AllWave 23. The wet electrolytic dried up and lost all its capacitance!

I am running the 721TS about five hours a day on weekdays and about four hours overall on weekends. That is about 30 hours per week. No sign of any problem with the original electrolytics.

Incidentally, CHCH TV in Hamilton Ontario is running Andy Griffith, I Love Lucy, Danny Thomas Show, My Three Sons and Bonanza between 10am and 1pm weekdays and the 721TS is on in the background as I work in my office.

Here is Bonanza photographed off air just now.

This my monthly update on the state of the original electrolytics. And the daily run of the RCA 721TS.

Still running fine. Here is a screen shot of a received morning broadcast just now of the Andy Griffith Show.

It has been about 5 months since I last reported on the 721TS. Still running fine on the original electrolytics after two years. Only problem with the set is the fine tuning backlash which is from what I see a common fault with the KRK2 tuner. Been running well over 1500 hours now.

Note it is sitting on top of my RCA AR88D receiver.

I just brought home a Crosley 9-408 tv that is all original with no repairs having been previously done. It looks nearly new especially the underside with it's numerous paper/wax capacitors. All the tubes are RCA with date codes ranging from the 11th-22nd week of 1948 with the exception of the two 5U4G's which are Sylvania.

I powered it up on a dimbulb tester with a 250 watt heat lamp and it passed that test. I also have an early RCA 630 TS that I electronically restored with the ever popular "shotgun" method of replacing all the Paper/wax caps and re-stuffing all the electrolytic caps. The set has been working quite well now for four years. While on the dimbulb tester I monitored the current draw with a kill a watt. The Crosley drew only a few watts less than the RCA.

The previous owner said the set worked and provided photographic proof. This mans father is a retired tv tech that fixed old tv's he is nearly 90.

I cautiously powered the set up on a power conditioner for a computer at a line voltage of 120 volts. I also hooked it up to a dvd player and applied a signal. After about 15 seconds I got a raster and after some fiddling with the brightness, horizontal, vertical and contrast I got horizontal and vertical sync and after a minute or so a fairly stable picture that looked quite good! Current draw was 295 watts, about 5 watts less than my RCA. I did not leave the set to run for more than a few minutes fearing that something might give out.

I was quite amazed that this was even possible! All the capacitors, resistors and even wiring looks nearly new. The resistors under the 1B3 have only a little dust and no carbon build up on them. I could even read the color bands easily after brushing the dust away. This set seems to have very few hours on it.

Unfortunately I don't have any tools for trouble shooting radio and tv other than a DMM which can measure resistance, capacitance, inductance, frequency and diode test. I do have a good digital soldering station.

The one job I enjoy the least is re-stuffing the electrolytic cans! After reading much of this thread I am convinced that it may not always be necessary.

Any suggestions? I will try to post some pictures of my set soon.

Thanks in advance!

Paul D.

I want to emphasize that I never power up electronic equipment of this age without first doing a full electronic assessment. As with the RCA 721TS, I assessed each electrolytic individually by isolating each electrolytic and reforming the dielectric.

I apply a power supply current limited to 10mA maximum and wait until the full rated voltage is met with less than 1 mA leakage. I typically aim for less than 500 uA. If the leakage after a day or so is 1 mA or higher, the capacitor will be replaced/ restuffed.

The 721TS electrolytics all showed leakage well under 500 uA at full rated voltage and tested correct capacity within 10%. I will say that surprised me. But with my six RCA TVs from the late 40's, I have only had to restuff/ replace three electrolytic cans in total.

The problem is suddenly powering them up after a long dormant period without reforming will place undue stress. But I would be game to monitor current leakage over say a week of full rated voltage to see if they survive and if so, I would not hesitate in leaving them in place.

My 721TS has been running on the capacitors for two years now with no sign of failing despite warnings from others.

21 June, 2020

No sign of any problem with the original electrolytic capacitors since they were reformed. I shall intermittently keep the set on and keep an eye on it.

It has been more than two years running regularly. The original electrolytics remain fine.

I was told the original electrolytics would eventually fail. Any suggestions when this will be?

Well it has been exactly two years and three months of regular operations. It was June 20, 2020 I first powered it up. It has been running fine ever since. And I am still waiting for those danged original 1947 vintage electrolytic capacitors to fail. There are five of them and they just won't go bad!

I am beside myself because I was sure they were going to fail by now.

Anyhow here is a photo I took a few minutes ago.

That's encouraging since I have an RCA 630TS that I purchased a few years ago. It is in great condition; the GE replacement CRT measures NOS. I guess I should bring it up slowly on my Sencore PR-57, monitoring the current and see what happens. I don't mind rebuilding the capacitors but if they hold good, why not???

Thanks for the encouraging update.

That's encouraging since I have an RCA 630TS that I purchased a few years ago. It is in great condition; the GE replacement CRT measures NOS. I guess I should bring it up slowly on my Sencore PR-57, monitoring the current and see what happens. I don't mind rebuilding the capacitors but if they hold good, why not???

Thanks for the encouraging update.

You could do it slowly that way. What I prefer is to put a current limited DC power supply across the electrolytics with power off. With the tubes not conducting and with a study of the schematic to see what bleeders are across the B plus, you can better gauge the condition of the electrolytics. In some cases I simply disconnect the electrolytics to better isolate to confirm the condition of the electrolytic.

I have restored set that must have been dormant for 50 years of more. My RCA 721TS the seller near Schenectady NY told me my 721TS was stuch in the attic in the early 60's and was not touched until they sold it to me in 2016. I cleaned out a mouse nest but didn't start to restore it until 2020. It absolutely had not been powered in the meantime so it likely sat unpowered for 60 years. Incredible when you think about it.

And that is what I think saved the electrolytics. I gently brought up the capacitors by limiting the current to no more that about 10mA per capacitor. If the set has sat for decades, the capacitors will be almost a dead short and it is almost certain the capacitors will be destroyed. Yhe key is to carefully monitor and ensure the current is strictly limited until the dielectric has properly reformed.

I would leave the DC supply on for the night and inch the voltage upwards while monitoring the current. When it reached close to the rated maximum voltage, the electrolytic, if healthy, it will draw only about 100uA. If the capacitors draw more than 1mA after reforming, then it must be restuffed.

To summarize, I do not like using a Variac to first power up. To me it is the lazy man approach to the problem and because you are more adequately monitoring the current, it is hit and miss. By using a high voltage DC supply with current and voltage monitoring, you can better decide whether the capacitor is a survivor or not.

Proof should be the 721TS which has lasted over two years on ALL the aluminum can capacitors. I am in the midst of restoring a CT100 color set (which when I have time again in a few weeks will get down to the final alignment) which I slowly reformed the capacitors with the DC supply. All have survived and work fine.

You could do it slowly that way. What I prefer is to put a current limited DC power supply across the electrolytics with power off. With the tubes not conducting and with a study of the schematic to see what bleeders are across the B plus, you can better gauge the condition of the electrolytics. In some cases I simply disconnect the electrolytics to better isolate to confirm the condition of the electrolytic....

I have a Heathkit High Voltage Power Supply, IP-17 which I have totally restored. It has voltage and current meters so it would be easy to do.

I have a working T100 that came up on all original electrolytic capacitors. But I have not turned it on for about 8-10 years though. It was rather easy to get going.

I have a Heathkit High Voltage Power Supply, IP-17 which I have totally restored. It has voltage and current meters so it would be easy to do.

I have a working T100 that came up on all original electrolytic capacitors. But I have not turned it on for about 8-10 years though. It was rather easy to get going.

8 to 10 years off, if the capacitors were previously good, I dont think will be a problem. I think it is a problem when it has been off for 40 or more years with a sudden power up..

If you use the DC HV power supply across the B plus line to reform the capacitors, I will be interested in your results.

The set has now been running faultlessly since July 2020. That is two and a half years still running on the original electrolytics. Still no sign of failure.

Great to see this update and you have given me an incentive. I have an RCA 630TS that is in excellent physical condition and has all of the parts. The GE CRT, no doubt a replacement, tests NOS. I will start with replacing the paper capacitors in the sweep sections and audio and see how the electrolytic capacitors reform. Carefully, slowly! Thanks.

It has now been three years since I resuscitated this set. Recall all of the original electrolytics except for a replaced 40uFd axial lead unit are original. Most of the paper dielcetric capacitors were changed. I left a few units which were bypassed by resistors less than 100Kohm. And a few resistors which I found drifted when it affected performance. I then decided to run the set regularly and report from time to time on it's performance over the years. It is well past 1500 hours.

The set has developed two problems:
1. The original KRK2 tuner fine tuning has a bad back lash which make it difficult to fine tune. I believe it has to do with the slop in the shafte which I have to address. The second is a horizontal sync issue which causes the horiztal oscilaator phase to shift briefly and jump back. It is very momemtary and occurs rarely. Have no idea what it may be and keeping an eye on it.

But this set has been incredibly reliable and delivers a very good picture for a set which is 76 years old. Here are a few snapshots from over the air CHCH TV channel 11 this morning.

Latest update on the 721TCS.

From the original 2020 restoration:

All the original can electrolytics are still fine with no problem That makes them 76 years old!

I left many of the original wax capacitors which pose no threat due to leakage. The ones I left are shunted by resistances 1M ohm or less and pose no DC threat.

Only two resistors changed asthey affected performance (horizonal plate resistor and video amp plate resistor.

An axial lead 40uF capacitor changed due to leakage.

Recent service:

KRK2 tuner fine tuning problem - slop due to wear in the brass tuning wand worn making it hard to tune for best sound (recall this is a split sound set). I made a new brass wand and attached it to the original tuning shaft disc. The repair fixed perfectly the fine tuning issue.

Horizontal jumping. the picture would jitter horizontally due to what appearred to be a time constant change in the circuit. Changed 6SN7 oscillator tube which fixed the problem.

Set remains working fine after regular 3 1/2 years use on all original electrolytic capacitors.

Here is a screen shot from this morning with the signal from an over the air signal via an ATSC set top box.

...
Here is a screen shot from this morning with the signal from an over the air signal via an ATSC set top box.

Beautiful!

Latest update on the 721TCS.

From the original 2020 restoration:

All the original can electrolytics are still fine with no problem That makes them 76 years old!Interesting.

I recently restored (But did not align) my 630TS and found that half of the original electrolytic capacitors tested good (out of circuit) for leakage; the other half were no good. I restuffed the bad ones and reconnected those testing good. I could see that those which tested good were a different manufacturer (or design or whatever, just different). Sure made things easier.

I guess they may be from the same era/manufacturer?

Interesting.

I recently restored (But did not align) my 630TS and found that half of the original electrolytic capacitors tested good (out of circuit) for leakage; the other half were no good. I restuffed the bad ones and reconnected those testing good. I could see that those which tested good were a different manufacturer (or design or whatever, just different). Sure made things easier.

I guess they may be from the same era/manufacturer?

The capacitors in this 721TS initially looked bad. But the set had been stored away and left dormant for 55 years when I bought it. I slowly reformed the capacitors over the course of four days. The key is to limit the current to just under 10mA and slowly bring up the voltage until it meets or slightly exceeds the maximum rated voltage. I would then let it sit at the maximum voltage for a few hours and notice the current continue to drop until it was no more than 200uA at maximum voltage. All of the capacitors came back that way.

However, I have a Canadian market RCA CTC5 color TV. The set was manufactured in Camden NJ and in Montreal it was modified for 25Hz power. The modification included replacing the power transformer on the main chassis with a 25 Hz filament only transformer and then adding a separate small additional chassis with a massive B supply transformer, an additional filter chole plus two Canadian mad Sprague 80uF 500v electrolytic capacitors. The main chassis had Camden installed Mallory capacitors.

When I restored the set in 2014, the Mallory capacitors reformed dielectrics were very low leakage 100uA or less. The Sprague's were close to 1mA leakage at 500v. I left them in and 8 years later one shorted and destroyed a pair of 5U4 rectifiers. I felt at the time the Sprague's were marginal. But the Malloys remain fine.

It has just reached four years since the restoration. The restoration preserved all the original chassis mount electrolytics and carbon resistors. Only the paper capacitors not shunted by resistors were replaced.

Sixteen paper capacitors and an axial lead 40uFd and capacitor were replaced. Two out of tolerance were replaced with identical type carbon resistors.

The only mechanical issue was a loose worn brass fine tuning shaft which I remade and replaced. A full IF RF alignment was done.

I switch on the set regularly and it remains in excellent operating condition. The snapshots are from an off air signal this evening.

The aim of this thread was to see if the original 77 year old electrolytics would stand up to modern use. As I pointed out earlier in this thread, I took care reforming slowly the original electrolytics.

Impressive. And equally impressive is the lifetime of these electros!

Looks good of course. I have a 630TS that still has one half of the can electrolytics original. The other half of them were leaky and were rebuilt (stuffed). I found that the ones that are still original were manufactured by the same company; the ones that were leaky were manufactured by a different company. I don't know who the companies were, only that I could tell by construction materials, technique etc. were the same.

Thanks for sharing!

That is what I found with RCA CTC5 Canadian chassis. The Camden installed Mallory's remained all good. But the Canadian Sprague capacitors mounted on the auxillary 25Hz chassis were bad and refused to reform without appreciable leakage.

Recall I spend a few days slowly reforming the capacitors after the TV sets and remained dorment and unused for many years. Most would come up fine but there are a few that will have a higher leakage. The Spragues becan with a leakage of about 1mA and that current leads to heat dissipation which propagates eventual catastrophic failure. I waited to see what would happen to the Spragues and they were warm in operation. If the capacitor is warm, it will go!

So far the 77 year old units in the 721TS still run cool after an hours operation. So my suggestion before even plugging the set in is to do an assessment and dielectric refomation to ensure leakage is 100uA or less and then give them a try.

Yes, it is interesting.

I know that it's a PITA but if there are not a lot of connections on the electrolytic capacitor, I disconnect every lead and test the capacitor for value first and leakage at the working voltage next. If it passes, I put everything back and then monitor the temperature. Sometimes you win, sometimes you lose.

Yes, it is interesting.

I know that it's a PITA but if there are not a lot of connections on the electrolytic capacitor, I disconnect every lead and test the capacitor for value first and leakage at the working voltage next. If it passes, I put everything back and then monitor the temperature. Sometimes you win, sometimes you lose.

When I bought this set about 6 years ago, it had sat in an attic for nearly 60 years unpowered. Apart from a mouse nest, it was a pretty clean and intact set. When I began the restoration, I decided to first evaluate the electrolytics. As it had not been powered on for many years, the filter capacitors were extremely leaky. I believe had it been powered as I found it, the capacitors would have been most likely destroyed and the rectifier destroyed.

I proceeded to reform the electrolytics by simply removing the 5U4 rectifier and with power off, connecting my Sprague TO6 supply across the B+ supply line. I limited the current to a maximum of 10mA and left the TO6 running all night. The voltage across the capacitors began to rise from less than 10 volts @ 10mA. I had taken into account any shunt resistance across the B supply and I recall removing some divider resistances.

The next morning the capacitor voltage had reached nearly 100 volts with minimal leakage. I raised the voltage and keeping maximum leakage less than 10mA. By the end of the day the total paralleled capacitor leakage was well under 1mA. I disconnected a few capacitors I could not readily access to ensure leakage was no more than 100uA at full rated voltage.

The point I am making here is that the capacitors will be destroyed unless a more gentle approach is made waking them up. I never use a variac to power up an old device. I will instead immediately look at the electrolytics and evaluate and see if they will reform. Then if the TV set dates prior to 1960, I will replace almost all the paper capacitors.

I have rebuilt a sizable number of electrolytics which will not reform. But with all 5 of my late 40's RCA Televisions, I have only replaced one chassis mount multiple section electrolytic. My CT100 had two bad chassis mount electrolytics and my CTC5 set has retained all the original electrolytics. Curiously, a 1961 CTC 11 RCA color I restored a decade ago required replacement of every chassis mount electrolytic. All but one the dielectric would not reform and the one that did suddenly failed in service. (The failure was not a short but went totally open.)

So there is no hard and fast rule. It is easy to reform the things and to test leakage and capacitance. And the experience I have had has been very good up to now.

When I bought this set about 6 years ago, ...

So there is no hard and fast rule. It is easy to reform the things and to test leakage and capacitance. And the experience I have had has been very good up to now.

And that's the key. No two are alike.

Just an update after 4 1/2 years of regular use. Only problem in the last 4 1/2 years was the KRK2 fine tuning shaft. I made a new one out of brass riveted to the original fine tuning disc.

Still using all of the original chassis mount electrolytics. 78 years and still fine. The restoration entailed only replacing the wax caps that needed replacing eg subject to a a large DC across them. A three resistors had drifted affecting operation. Tested transconductance on all tubes and replace a few with original period NOS RCA tubes.

The main point is the originality of the electrolytics. They survived because the set was not plugged in after the set sat unpowered for over 50 years. Slowly reformed the capacitor dielectrics and they are all still fine. One axial lead electrolytic was bad and was replaced.

Here are a couple of snapshots off air made this afternoon. Can you name the film?

Thought I should resurrect this old thread considering the significance of the originality of my 1947 721TS. I resuscitated this set nearly 5 1/2 years ago and this was to be an experiment to see if a fairly well preserved set could be reliably operated replacing parts only what were absolutely necessary.

In the resuscitation of this set, it retains all but two of it's carbon resistors. About 95% of the paper dielectric capacitors were changed. The ones that were retained were shunted by resistances which swamped the leakage resistance of the capacitors. It retains some of its original tubes. I carefully selected RCA period tube for replacement so it is a fully RCA tubed set. When I received the set 10 years ago, it had sat in a heated attic in a house near Schenectady for just over 50 years. Upon pulling it apart I found a small mouse nest under the chassis and fortunately it caused almost no damage. The set was not powered from the early 1960's until after it's resuscitation in 2020.

However, of major consideration is this set retains all of it's original electrolytic capacitors. This thread describes the extra effort I took to preserve the capacitors. I am not averse to changing the electrolytic ic they test bad. But slowly reforming the dielectric on each electrolytic in this set brought them all back with very low leakage.

So the bet was on as to how long they would last? I power the set on average once a week and let it run for a couple of hours. I decided to check the capacitors this evening and can report that they all appear fine.

Here after 5 1/2 years, after the careful reforming of all the original electrolytic cans, are some off air shots. (I did replace the original 40uF axial lead electrolytic but all the chassis mounted cans are now 78 years old.

Gorgeous pics!

Thanks.

"The Lady Vanishes".

I notice this thread return today. I have a comment on electrolytics.

Earlier this year I opened up and checked the electrolytics on a ~1975 device I have that has run with no repairs for over 250000 hours. They check out fine, low leakage, low ESR, and within spec capacitance. This set ran continuously except for long vacations for over 30 years. It is a Hafler 280 watt audio amp. I also checked the amp's performance, and it meets specs.

Just to be sure, the words are "two hundred fifty thousand hours". The caps are mounted well away from the transformer and heat sinks, and it has been well ventilated.

I’ve had the same experience with equipment that used Sprague Atonms The blue aluminum electrolytics with axial leads. I used to own a dental laboratory which I opened in 1980. One furnace that I fire porcelain in heats a small chamber to 2000 degrees F. Since it was installed it’s never been turned off except for a week or two during vacations. It’s well ventilated with heat sinks to protect critical components. I’ve never bothered to check the capacitors as it still works the way it should nearly 50 years old now.

Next month it is 6 years since I reformed the electrolytics. I still regularly use the set and all the chassis mount electrolytics remain fine.

Recall the set remained in an attic for over 50 years unpowered. I attribute this the electrolytic capacitor survival to slowly reforming the dielectric. When the capacitors have been reformed, the current should be no more that 200uA at full rated voltage.

Note when I began reforming the capacitors, each began as a near dead short. The initial 10 milliamperes was reached at about 15 volts! Over a period of about six hours, the current dropped slowly until after six hours, the current was 200 uA at the capacitor full rated voltage. Periodic testing showed that the current remained at around 200 uA which is normal for these types of electrolytic capacitors.

Here are some photos 721TS this morning on it's 79 year old electrolytics. The video source this time is a VHS tape of of the motion picture "Mr Smith Goes to Washington" played on my 1977 RCA VBT-200 VHS machine: the first VHS machine introduced to the US market.

:thmbsp:

It was six years ago in June 2020 I restored this set.

To recap, I intended to make this a thoughtful restoration. That is I only replaced what was absolutely necessary. I would only replace what I felt necessary to affect the operation of the set.

I attempted first to reform all the electrolytics. Amazingly all the chassis mount can electrolytics reformed well with minimal expected leakage. An axial tubular 40uF.electrolytic used as the audio output screen decoupling capacitor was bad and replaced by a modern unit.

I next used my transconductance tube tester to check and replace weak and defective tubes.

Analysing the circuit, I next only replaced the paper capacitors that were not shunted by a low resistance. In other words, if the capacitor was in a high impedance circuit or there was a high dc voltage normally across it, the capacitor was replaced.

Lastly, resistors were only replaced if they caused impairment to the sets operation. After the capacitors were dealt with and when the set was powered, I would look for any obivious operation faults which would point to a bad resistor. Then even if there was no apparent fault, I would measure and compare the voltages recorded in the RCA service notes.

In the past six years, I expect it has operated for about 2000 hours. The only issue I have had was a worn 1/4" brass fine tuning shaft. the excessive play made it difficult to fine tune. Recall this is a split sound non-intercarrier set and tuning for best sound was difficult. The solution was replacing the brass shaft on the KRK 2 tuner variable capacitor. That was two years ago and it remains excellent since the fix.

Here are a couple of snapshots from tonight's Saturday Night Live.

:thmbsp: