Decided to have a go at my 9T246 that's been "on display" since I picked it up over the summer. Powered it up on a variac when I got it, and while the raster was bright, the picture was a distorted mess. Today, as the wife was baking cookies, I went as far as the capacitors I had on the shelf would take me, and this is what I got!

Clicking the picture will take you to the video :)

http://i44.photobucket.com/albums/f9/hondacuraworld/th_100_2418.jpg (http://s44.photobucket.com/albums/f9/hondacuraworld/?action=view&current=100_2418.mp4)

Weird problem though. If I leave it on the channel that was on when I turned it on, the set is fine. As soon as I change the channel, the picture loses horizontal sync. Otherwise, I just watched a full episode of Gunsmoke on the thing.....

If I turn the set off for a half hour or so, then turn it on, the channel I left it on is fine.

Ideas/thoughts? Obviously I'm going to have to order the rest of the capacitors and finish the re-cap, but this is something I haven't seen before.

Dah-Yum, Tim, for just "Foolin' Around" that's pretty dad-blame good..

I got lucky :para: :D

Yeah, maybe so, but you're also pretty GOOD, too...

there is a rather involved setup of the sync, adj the horz coil top and bottom, then the sync drive cap. Clearly you need to to all the caps and would be a good idea to replace the domino style caps in the horz circuit as well.

You are also living dangerously with original electrolytics, and, those black beauty striped capacitors. I've seen them explode.
I've seen electrolytics explode, and, do other nasty things. I had one in a 9T246 that actually shorted to another section. Result. smoke for an angry resistor, and, the set still lit picture tube, but, lost all reception, and, I couldn't turn down brightness control. That circut was shorted when the cap shorted to another section.
If a filter blows, yo'll blow your resistor bank on the back of the chassis. Then what will you do??
Bill Cahill

Good Job Tim, you're on your way to working history. Lets see more.

That's looking pretty good.:thmbsp: There's a good chance that replacing the rest of the caps will help the sync lock in better, then make the horizontal waveform adjustments as Dave mentions.

Yup. And make sure you replace the molded paper caps along with all the tubulars and electrolytics.

I would also replace the silver micas in the horizontal sweep section, as those seem to be failing nowadays.

Then, check the tubes and high value resistors, and tweak the set with a Test Pattern.:smoke:

http://i268.photobucket.com/albums/jj7/300cSRT8_photos/NEW%20RCA%20Victor%20630TS%20Resto/NEW630TSFinalAssembly018.jpg

So, basically, I just need to finish the job :) . Kinda figured that was the case, it's just that I've never seen something like that happen before. Left on channel, I had it playing for about a half hour with no issues. Change the channel at any point, and all of a sudden, bye bye horizontal sync.

Time to order capacitors :)

I am still amazed that everyone in this forum insists on always replacing the electrolytics. The original electrolytics used in the RCA sets of the period will probably outlast the ones being stuffed into the cans!

It is a simple process reforming the dielectric and testing the things. I have replaced some electrolytics if they do not reform properly. The test is to ensure the leakage current remains below 100uA at full rated voltage.

Paper capacitors do leak and need to be replaced. When I get a set and before powering it up, I will test a few of the paper capacitors. If any show leakage (as they generally will) I will replace all of the. However, the electrolytics and micas are generally okay.

I am still amazed that everyone in this forum insists on always replacing the electrolytics. The original electrolytics used in the RCA sets of the period will probably outlast the ones being stuffed into the cans!

Hmmmm....No. I disagree.

You can get 105 centigrade rated electrolytic caps from Mouser that are light years ahead of anything they made in 1946. Cheap money, too.

Were the 'lytics that RCA used in '46 good? You bet. Are they any good now? Do you really want to roll the dice and worry about it? Plus, the micas in the hor sweep circuits are starting to fail. I habitually replace those now, too.:smoke:

http://i268.photobucket.com/albums/jj7/300cSRT8_photos/NEW%20RCA%20Victor%20630TS%20Resto/NEW630TSResto-ChassisFinished003.jpg

http://i268.photobucket.com/albums/jj7/300cSRT8_photos/DuMont%20RA-119%20Royal%20Sovereign/DuMontRA-119A-Picture-R155Uppedto25K002.jpg

I am still amazed that everyone in this forum insists on always replacing the electrolytics. The original electrolytics used in the RCA sets of the period will probably outlast the ones being stuffed into the cans!


Have you ever cut any of them open?
Most electrolytic caps from 1950 and earlier that I restuffed were dried out and crumbling, the foil was deteriorated and rotted not to mention the leakage between sections.

Occasionally I will find some that still work but knowing what they probably look like inside there's no way I'd feel comfortable using them.

Yah, the innards of 1940s electrolytics are usually nasty. The photo shows a can from my 1948 Capehart-Farnsworth 661-P.

That one came out mostly in one piece. Some come out with a bunch of dust and crumbly chunks.

I don't care if anyone else replaces electrolytics -- it's your TV, do what you like -- but I'm not comfortable running with that kind of component onboard.

Phil Nelson

http://www.antiqueradio.org/art/Capehart661-PPart912.jpg

I am still amazed that everyone in this forum insists on always replacing the electrolytics. The original electrolytics used in the RCA sets of the period will probably outlast the ones being stuffed into the cans!

It is a simple process reforming the dielectric and testing the things. I have replaced some electrolytics if they do not reform properly. The test is to ensure the leakage current remains below 100uA at full rated voltage.

....

Yikes! Did I read what I think I read? Sorry, I have to respectfully disagree with this as others have...

Double Yikes!!:eek::jawdrop: I read it too, and dunno what to say. So I guess just don't say nuthin'.

I'm gonna go through and replace them. That was my intention from the beginning. Leaving them alone is okay if you want to just off the set as "working", but if you want to actually USE the set, you might as well just leave the chassis sitting on the bench, because chances are they're gonna fail anyway.

Parts are on order :)

Weird problem though. If I leave it on the channel that was on when I turned it on, the set is fine. As soon as I change the channel, the picture loses horizontal sync. Otherwise, I just watched a full episode of Gunsmoke on the thing.....

Horizontal sync that locks as the set warms up, but won't relock after a channel change is a relatively common problem on the early RCA sets using this and similar horizontal circuits.

The cause is misadjustment of the multiple controls in horizontal sync.

I don't have a factory schematic on this set, so take look at the Sams 74, fol 8:

http://www.earlytelevision.org/pdf/RCA-8T241-Sams-74-8.pdf

If the .01 Mfd cap on the exposed end of T3 Horizontal Oscillator coil under the chassis is original, you can bet that this set was taken out of service before it was 10 years old. But, you say, this cap is paralleled by a 22K resistor, how could a little leakage hurt? Well it can cause some well-intended person to mess up the other horizontal sync adjustments!

After you have finished recapping the set, follow the alignment procedure on page 18 of that Sams. If you are lucky, you won't have to use a scope.

But if you have (or can borrow) a scope with a low cap probe, and you make the final adjustment and then repeat the full page 18 procedure to even things up, you will find that these early RCA sets were some of the most stable sweep sets made during that era.

Today we take for granted that the TV signal will be stable. Remember when this set was made, when ever the station switched from network to local, there was a slight time-shift in the sync. On the smaller stations, often the film chain would also be slightly off with the studio cameras, and location footage would be even more off. These circuits kept the RCA sets from rolling on scene changes, unlike the sets from many of their competitors.

Re: Mica caps

Try to avoid bending the leads of the old ones. This seems to start problems.


Re: Electrolytic caps

If you decide to keep the original electrolytics, add fuses ahead of them to kill the power when they fail.

I won't join the argument on replacing electrolytics, but I am more inclined to leave a pre-1960 one in for set testing (only after disconnecting it and reforming) than a post-1970 one in any circuit. Either way, restuff or replace, carries a definite risk unless you can find relatively new industrial or military grade electrolytics. I am unimpressed by the quality of currently available electrolytics for tube-era voltages. They seem to be made to last the length of the warranty.

James

James, thanks a TON for that useful information. The project will resume as soon as the parts arrive :) .

For the capacitors, this is what I plan to do. I did this work on a '52 Motorola as seen in this picture. While it won't be popular to the purist, I intend to use the snot out of this set when I'm done, and to me, serviceability is the key. I have no intention of restuffing them, and letting loose caps dangle on the underside isn't really appealing......there's no real room to do an under-chassis mount in these areas.

http://i44.photobucket.com/albums/f9/hondacuraworld/100_5093.jpg

Another shot of the '52 Motorola. See how it cleaned things up under the chassis?

http://i44.photobucket.com/albums/f9/hondacuraworld/100_5094.jpg

Thank you for the replies! I respect your disagreements. The philosophy of simply replacing a component because everyone does it seems odd to me. I have seen my share of bad electrolytics. I just want to point out you can easily test and measure whether an electrolytic will hold up and whether it is good or bad.

The test is simple: reform the dielectric and measure the leakage current and capacitance. The reforming of a capacitor takes a few hours and I will put the full rated DC across it for a few days. If the leakage is more than 200uA, then it must be replaced. 200uA is far below the point of creating any heat dissapation from the capacitor. If you detect a 450v capacitor getting warm, then the leakage will more like 10000uA or above.

The RCA set capacitors used from the KCS28 chassis upwards are extremely good. Of the six sets of the late forties and early fifties vintage I have restored over the last 40 years, I have replaced two electrolytics. And the ones replaced never shorted, they became open. I have never had an old electrolytic explode as a result of the precautions I have taken. I have however seen newer capacitors explode.

The measure of pulling one apart and it looking crumbly and bad is no judge of its condition. Dry electrolytics use a dry paste and even a good one will crumble upon taking it apart.

Then again if you feel uncomfortable about this, by all means pull the old capacitor apart and stick in newer replacements. Also, if someone has been foolhardy to plug in the set after it has remained doment for 40 years, then you should expect explosions and fireworks. By my monitoring procedure I will find if a capacitor has been stressed.

I would just like to reitterate that I find it unfortunate that the assumption is that a component must be replaced without even testing the component to see if it is bad.

I won't join the argument on replacing electrolytics, but I am more inclined to leave a pre-1960 one in for set testing (only after disconnecting it and reforming) than a post-1970 one in any circuit. Either way, restuff or replace, carries a definite risk unless you can find relatively new industrial or military grade electrolytics. I am unimpressed by the quality of currently available electrolytics for tube-era voltages. They seem to be made to last the length of the warranty.

James

When I replace electrolytics, I use the good 105 degree C Nichicon and Panasonic caps, and exceed the origional voltage ratings by wide margins. I usually double a 25v rated 'lytic with a 50v, and for 250v I always use 450v, etc.

I like overbuilding these TVs when I restore them. The last thing I want to do is open them up again when I'm finished tweaking them.:smoke:

The last thing I want to do is open them up again when I'm finished tweaking them.:smoke:

Amen.

Well that seems weird, for me, the opening of them up is the fun part. :D It's at least way more interesting than changing the oil on the daily driver.

You guys might find this webpage from Illinois Capacitors interesting (http://www.illinoiscapacitor.com/tech-center/life-calculators.aspx). It has capacitor Life Calculators for electrolytic, film and ceramic capacitors.

It quantifies the advice we've seen nicely. Voltage derating does indeed increase the life span. Using 105C rate caps extends them considerably more though.

Typical general purpose caps have a 1,000-2,000 hour life at maximum temp and voltage.

Nichicon has a new line (http://www.mouser.com/search/refine.aspx?Ntk=P_MarCom&Ntt=109379352) out of high ripple, long life caps rated for 450 volts, 105C and 10,000 hours. They also have a very small diameter and great for restuffing cans.
http://www.mouser.com/images/nichicon/lrg/pzcs.jpg

Use one of those at 300 volts, keep the temp down to 50C (122 F) and it should last about 675,000 hours or 77 years of continuous operation :)
Using a cap with the same ratings except 85C should last about 169,706 hours or 19 years of continuous operation.

Amen.

Well I have owned a set with esentially the same chassis as the 9T246 since 1969. I have since replaced all the paper capacitors, the AGC and sound discriminatorelectrolytics, a few resistors and a number of vacuum tubes since 1969. But all the power electrolytics still function as originally designed.

To each his own. I prefer to keep the sets as original as possible and I can assure you that I do not have to pull the chassis because of electrolytics.

I suggest you prove it for yourself. Take an old electroltyic from a 40's or 50's era RCA TV, reform the dielectric as I suggest and measure the leakage current. You will find that rarely do these capacitors go bad.

And consider this: if after 50 years the above test shows that a capacitor is still good, would this not suggest that the new capacitors that are currently used for replacement, may not last as long?

I have tried it myself on sets from the 40s - many times. Easily 75% are open due to a deteriorated electrolyte and cannot be reformed. I also find many original electrolytics have already been replaced back in the 50s.

But one would have to assume the odds would have been much better had you gotten into the hobby back in 1969. I think the longer they sit idle, the less likely they are to recover.

I've hacksawed off old can electrolytics near the base, the location just above the fat part at the base. That fat part holds a rubber gasket, which holds the terminals down below the chassis, and has wires passing thru to go to the actual cap guts. Clean off the top of this rubber gasket, and then either mount new caps to the terminals below the chassis, or drill small holes to pass new cap leads so you can mount the new caps topside and have the leads connect to the appropriate terminals below. If you're lucky you can slip the empty can over the new caps on the topside. Put one or more caps down below if they don't all fit. One advantage is that you don't have to undo the wiring on the terminals.

since we are talking about caps, I decided to test out reforming a NOS 3 section.

150 @450v
100@400v
100@50v

I started out at 25v, the eye quickly opened, I jumped up to 150 pretty quick and again it opened pretty fast. I have it sitting at 250v now and its about .2ma of leakage (have a DMM in series with the cap eye tester). I will leave it there overnite and jump up to 350v tomorrow and the 450v later in the day.

I will check for leakage between terminals later, and then will leave it alone for a couple of weeks and see how well it performs. I have a big box full of these NOS caps, I had orig planned on using them as base donors but I like to experiment.

I personally do not replace a can cap automatically, like Pentode, I try to reform them out of circuit 1st, if they compare to like new caps I just reconnect them and then fuse the B+

I did a recent project where I did this on a 8t241 chassis, replaced all the wax paper caps and a few of the horz mica (after having some horz issues).

All the cans were reformed and tested fine, some had been replaced some were original.

I am not trying to say its wrong to replace them, but I prefer to do what it takes to get the set running and then trouble shoot issues as required. different strokes for different folks.

I spent a few hours this afternoon trying to reform a dual 40mfd @450 from the 1948 set I'm currently working on. I was able to eliminate leakage but there's another problem I've encountered before. The capacitance is a small fraction of what it should be. I figure the electrolyte has broken down and it's just not doing it's job properly.

So I'm curious - when you guys reform them are you also checking the capacitance and is it within spec ?

yes, and the power factor as well. For the most part the test well over like 50%, if it was under I would reject it outright. I like to compare them to new caps, they generally test higher value, about the same in power factor, and up to about 2 to 4 times the leakage (but its still very low). I used to have a chart that was used for acceptable leakage.

It would not be uncommon for me to take more that 24hrs for one section. Is this really needed, maybe not but it cant hurt to try and besides like I said before it appeals to my interest in experimenting.

What I would really like would be a test setup that I could program to step up the voltage based on current, say have it ramp up to try and maintain a set constant leakage current (selectable), then graph that voltage over time and set the max voltage to end the test. The resulting curves would be fun to examine.

you could do it with a constantly variable DC power supply and a current meter (analog would be easy to watch) but I dont really want to stand by the PS and work that for however long it may take.

all the sections seem to have responded well to reforming. I will set it aside and check it in a couple of weeks.

While I understand the premise behind reforming the electrolytics, if you've got a set that you actually want to watch, isn't it easier in the long run just to replace the stupid things? :dunno:

Just like WA2ISE, I have a box full of removed multi-section cans. A few weeks ago, I tested them on my EICO 950. Almost every one of them had at least one open or leaky section. While the open caps are done for, the others could be reformed. Having never heard of reforming before following VK, I have RCA 721TS and 8T241 that I could try this on when I finally get to them. I also plan to fuse them pretty tightly as well!

For sets that are not what we consider "classics" and most of my 30's radios, I generally leave the old ones in, disconnect and solder new ones under the chassis. If someone has the time to refrom or restuff them in the future. At least they look original from the top.

Now you see 'em...

http://i268.photobucket.com/albums/jj7/300cSRT8_photos/RCA%20721TCS%20Resto/RCAVictor721TCSResto011-2.jpg

Now you don't...:smoke:

http://i268.photobucket.com/albums/jj7/300cSRT8_photos/RCA%20721TCS%20Resto/RCAVictor721TCSResto012.jpg

To further belabor the reforming of an old electrolytic capacitor discussion :boring:, the reforming takes time, especially if the capacitor has remained dorment.:scratch2:

Last year, when I restored an RCA 9TC275 (1949 with a 16AP4)) according to the original owners, the set had sat in a basement since 1964 un used. This set was a good test case as someone plugged in the set and melted one of the 5U4's literally!!

I was curious if the capacitors could be revitalized after this abuse. I found all the electrolytics almost a dead short. I left in position each electrolytic can on the chassis and isolated the connections to individually test each capacitor. I used my Sprague TO-6 to reform the dielectrics one-by-one. Each electrolytic section took about two to three hours to reform. After replacing all the paper capacitors and a few other components (mostly bad tubes and resistors) I ran the set on the bench for a couple of weeks, keeping an eye on the electrolytics. A 40ufd section of a multi-section capacitor opened and i replaced it with a new old stock multisection unit (after reforming it). I now use the set almost daily and it is reliable without any capacitor issues.:thmbsp:

What must be remembered is that even the dry electrolytics have a healing property. The crumbliness when disassembly is normal and does not necessarily mean the capacitor is bad.

Incidently, I am still working on my CTC5 and it was another long time dorment set with shorted electrolytics which reformed nicely apart from two Canadian Mallorys which was part of the Canadian 25Hz modification. The US RCA original capacitors all restored fine and are healthy with leakage below 100uA at full rated voltage.

I would encourage all to consider at least testing the components before condemning them.

Saying that, I have also done my share of restuffing over the years. My method is to slice the can about half an inch higher than depicted above. That is, about 1/2" above where the can becomes larger in diameter. I then obtain short section of aluminum tube slightly larger in diameter than the electrolytic and cut a 1" length. I then carefully slice it to remove a longitudinal section to reduce its diameter just enough to ensure a force fit on the inner diameter of the old electrolytic tube. I install new internal capacitors and then press fit with a vice the capacitor back together over the prepared 1"section of tube. The result is clean and barely perceptible from the original.

While I understand the premise behind reforming the electrolytics, if you've got a set that you actually want to watch, isn't it easier in the long run just to replace the stupid things? :dunno:

easier... maybe but not by much. I just disconnect the leads and hook up the variable power supply. after that I just walk away and check on it now and then. If they check out I reconnect the wires and its good to go.

I have MANY sets that are daily drivers, examples are my predicta and portacolor, the predicta had one bad can cap, the one with a low volt high value. the other two (a doubler and a mutisecion can that lays down in the back) checked out fine. I use it daily and its fine.

the porta color has its orig caps (1972 IIRC) its on for hours everday and I have had no problems at all with it.

I have a zenith CCII same story, and many sets from the 60's same deal.

I do of course come across bad caps, and when they test bad I replace them, but I do not just wholesale replace, I just dont see the need.

Besides frankly I sometimes wonder if the new caps will last any longer. I am not saying its right or wrong but it works for me.

When I do find a bad one, I use a bone saw, cut the can off at the shoulder, use a pin vice to drill holes from the bottom up, then put tall skinny radial caps in and solder them to the existing can terminals. Takes about 5 min per section so its fast, and I leave the orig lead dress alone. if there is a cardboard cover I will just put the now empty alum can back on and use the sleeve on to hold it, if no sleeve I use a little bit of 5 min epoxy around the edge (after cleaning it up).
The down side is the epoxy is not that strong a joint, so if at some time in the future, someone grabs the can like a handle for the chassis they may be in for a big surprise when it lets go.


after reading Pentodes method of using an expanding internal sleeve I will have to give that a try.

I have tried the uncrimp method, but that just takes a bit more patience than I have. the bone saw while crude is easy and quick.


I promise no more reforming on this thread, I don't want to come across as a zealot.

What I would really like would be a test setup that I could program to step up the voltage based on current, say have it ramp up to try and maintain a set constant leakage current (selectable), then graph that voltage over time and set the max voltage to end the test. The resulting curves would be fun to examine.


I threw together what you described above from Radio Shack stuff. It uses an Arduino Uno and a pulse width modulated motor controller to drive two 12.6V to 120V filament transformers to step up to 240VAC. Then a voltage quadrupler. This results in a programmable 6-900 VDC supply, The Arduino software reads the analog inputs to raise the capacitor voltage while limiting the current and max voltage, and then monitoing the current decline to the required minimum current. Anyway, here are some plots from four capacitors. I set the current limit to 5 mA, and the voltage limit to the cap working voltage. The first cap is a 630TS 40uF 450V, the second a Sprague 16uF 450V cap added as a repair, the third a 630TS 80uF 150V cap, and the last a Nichicon 82uF 450V cap. My Sencore LC75 says the RCA caps show a lot of dielectric absorption, the Sprague is toast, and the Nichicon was the best (of course, its new) but did also show some dielectric absorption. I thought it would be interesting to plot the computed power going into the cap as well as its computed effective resistance along with the measured voltage and current. Although its now controlled through USB, it could be standalone with the addition of a small two line LCD panel and some switches. I think I could save some of my 630TS caps, but some are completely unresponsive to reforming.

interesting graphs, would like to see both graph at 200 seconds. for 1 and 4

Also if you reran the test on the old caps does the graph change (reformed) so the low current target at rated voltage is reach sooner.


I looks like the 82uf took that long to hit max voltage, perhaps for reforming you could ramp down the current to say 1ma max. Very neat project.

interesting graphs, would like to see both graph at 200 seconds. for 1 and 4


Here is a plot of 1 up to 250 seconds. Is that what you mean?

Hi All;
I would like to see a circuit diagram ?? So, I can build one as well ..
THANK YOU Marty

And the SW for the Arduino...

Now you see 'em...

Now you don't...

Does anyone know if the black cardboard tubes you have used are available anywhere new or even new old stock?

I used to see them in the mfgr.'s catalog and in the radio supply stores but
no more. Seems like these would be a good sale item for restorers.

Cliff

Caps are cheap, why trust a nice old set to 50, 60 yr old caps that MIGHT have reformed, or maybe are just "Playin' Possum", as it were ?!?

Hi All;
I would like to see a circuit diagram ?? So, I can build one as well ..
THANK YOU Marty

And the SW for the Arduino...

I'll see if I can figure out how to draw a schematic using the free Eagle CAD program. I will need to clean up my rather messy code, but I will post it. I will make a new thread when I post them.

Hi All;
Sandy G., Maybe to you caps are cheap.. But, for me they are a major outlay.. It will take me a long time to come up with the funds for just the electrolytics, to say nothing about the paper caps.. Yea, I know, I just got the 630TS, which means I am going to have to sell alot of Stuff to make up for it..
THANK YOU Marty

[QUOTE=DaveWM;3058394]Also if you reran the test on the old caps does the graph change (reformed) so the low current target at rated voltage is reach sooner.
QUOTE]

I ran the reform process again on the two old RCA caps and attached are the plots. Yes, they got a better result from a second reforming. They both still show a lot of dielectric absorption, as seen by the LC75.

Hi All;
Sandy G., Maybe to you caps are cheap.. But, for me they are a major outlay.. It will take me a long time to come up with the funds for just the electrolytics, to say nothing about the paper caps.. Yea, I know, I just got the 630TS, which means I am going to have to sell alot of Stuff to make up for it..
THANK YOU Marty

The cost of capacitors will be a lot lower than the cost to construct this Arduino cap reformer. Although I may be able to save a few old electrolytic caps, most will still probably need to be replaced in my 630TS.

Hi All;
I asked about the reformer circuit for a couple of reasons.. 1. for all those beside me who would want to build one.. 2. I am cursious about what all is in it, maybe I have something else that is lying around that would work.. 3. Maybe someday I won't be a broke as I am now..
THANK YOU Marty

Yeah, the cost of the new caps would be INFINITESSIMAL compared to trying to find a 10BP4...or some other virtually Unobtainium component that gets destroyed because of a cap failure..

Hi All;
Yes, that is why I am in wait mode, and Not plugging in anything.. I couldn't afford replacing many of the items that would be vital.. But, I can do other things, like check tubes, check resistors, and the like.. Making a list of what is needed.. These are no cost things, that I can do in the meantime..
THANK YOU Marty

Yeah, man, I wasn't makin' fun of you or anything like that...Shit, Money's pretty damn TIGHT around HERE, too.. First thing, first, last & ALWAYS is SAFETY... NEVER get yrself hurt..Second is to always BE CAREFUL & make sure you're doing things right, 'cause you DON'T wanna "Woof" some expensive parts...Or even some cheap ones, for that matter..Thirdly, but maybe most importantly, in a way, is to try to PRESERVE these wonderful old devices, so FUTURE generations may marvel on them as WE do..Just think of the JOY some guy in the year 2150 or so will have owning an OPERATING 200-year old TV...Shit, they MAY pull out the 150 yr old Honda generator from the back of the cave & worship the snow on the raster...

Horizontal sync that locks as the set warms up, but won't relock after a channel change is a relatively common problem on the early RCA sets using this and similar horizontal circuits.

The cause is misadjustment of the multiple controls in horizontal sync.

I don't have a factory schematic on this set, so take look at the Sams 74, fol 8:

http://www.earlytelevision.org/pdf/RCA-8T241-Sams-74-8.pdf

If the .01 Mfd cap on the exposed end of T3 Horizontal Oscillator coil under the chassis is original, you can bet that this set was taken out of service before it was 10 years old. But, you say, this cap is paralleled by a 22K resistor, how could a little leakage hurt? Well it can cause some well-intended person to mess up the other horizontal sync adjustments!

After you have finished recapping the set, follow the alignment procedure on page 18 of that Sams. If you are lucky, you won't have to use a scope.



Well, the cap was indeed original....all of the wax caps have now been replaced with new mylar jobs. Since the set was working prior to this, I decided to plug it in at this point, and check my work. Everything's up to snuff, and the picture is much crisper than it was.....now for the last leg, the electrolytics.

The issue that brought about earlyfilm's post was my set losing horizontal lock when I change the channel, and having to power down the set for a period of time to get it to lock back in. The picture locks in fine as long as the set is left on the channel that it's set at when I power the set on.

Now I probably shouldn't have done this, but I did it anyway.....without a scope available, I applied the "golden screwdriver" technique, and tweaked B6 all over the place, using the rest of the controls to try to tune everything in......

Well, it worked, kind of. Whereas before I had to power down the set for an hour or longer to get the horizontal to come back, now I just have to flick it on and off, and it pops back into alignment. If I made any improvement, it was by dumb luck more than anything else. Picture size, linearity, etc, all seem close to dead on.

At the moment, the horizontal hold is at the end of its range clockwise....I can now bring it counterclockwise almost 1/2 turn without affecting the picture, and before I had to leave it buried to the right for the picture to lock in.

In the setup procedure, it says "If more than 9 bars are present Just before synchronization, turn the horizontal locking range trimmer (B5) slightly clockwise. If less than 7 bars are present, turn B5 slightly counterclockwise. Turn the hold control counterclockwise and momentarily interrupt the signal and check the number of bars present at the pull-in point. Repeat this procedure until 7 to 9 bars are present."

I never got down that low, there were about a dozen bars at best, maybe 20+ at worst. The horizontal locking range control seemed to have almost no effect on anything.

Something is telling me that I'm dealing with a resistor out of tolerance rather than a setup procedure, but I could be WAY off in that assumption. Thoughts?

[QUOTE=DaveWM;3058394]Also if you reran the test on the old caps does the graph change (reformed) so the low current target at rated voltage is reach sooner.
QUOTE]

I ran the reform process again on the two old RCA caps and attached are the plots. Yes, they got a better result from a second reforming. They both still show a lot of dielectric absorption, as seen by the LC75.

I see from your graph that full rated voltage is applied after only a minute or so. I believe this is too fast. I generally reform much more slowly and I use a limit the initial current to no more than 3mA. I will then leave the capacitor and return, say 15 minutes later, up the current again to 3mA step-by-step until the rated voltage is reached and the current reduces below 0.1mA.

I have reformed quite a few capacitors with a simple variable DC supply. (I first used an old variac, rectifiers and series resitance but now use my Sprague T06 capacitor checker).

I assume by diectric absorption you are referring to leakage? Certainly the older capacitors leak more than newer capacitors. But that was normal. What is important is the leakage is kept under control and that it remains low. I find gently reforming and lengthened testing results in a higher percentage of saved capacitors.

The leakage current scale on the graph is too high which does not allow you to see the resultant leakage current accurately. You must be able to ascertain that the leakage is below 0.2mA inn order to determine whether the capacitor is good or bad.

The resistance indication on the graph is interesting. Perhaps the fluctuation is the dielectric rebuilding process?

Now I probably shouldn't have done this, but I did it anyway.....without a scope available, I applied the "golden screwdriver" technique, and tweaked B6 all over the place, using the rest of the controls to try to tune everything in......



If you have the original RCA notes or the Rider notes, you can find how to adjust the horizontal blocking oscillator transformer without a scope.

The RCA Synchroguide oscillator circuit used by RCA and others for over a decade is quite straightforward to adjust. It comprised of the oscillator tuning adjustment and a separate sine wave stabilization coil. In the earlier sets, these were mounted on the same coil form.

In this set you are first told to short out the stabilzation coil (I believe terminals C and D) and adjust (under the chassis) to frequency. Because it is a blocking oscillator it behaves similarly to the vertical blocking oscillator in the way it locks. The best lock position for the horizontal oscillator is to sync at just the point where the sync bar just disappears to the left with this adjustment.

After adjusting the oscillator, remove the short from C and D. Turn the horizontal hold to the far left, interrupt the signal and you should find the picture out of sync. Adjust the sine coil (from outside of chassis) so that about five to seven bars are seen before it pulls into lock. The adjustments interact so that you may have to go over it a few times.

You can tell if the sine coil is misadjusted: if the sine coil is adjusted to far one way you will get double triggering and you will hear a "chipping" sound when you adjust the horizontal hold. Too far the other way and the noise immunity is lost: verticals in the picture will look coggly on weaker or noisy signals.

I do not think there is likely a resistor problem. You need to ensure the oscillator and sine wave coil are set up correctly first. I would simply leave the locking range trimmer at about 1 1/2 turn from fully clockwise and see to the oscillator first. These adjustments all interact.

Try and find the RCA notes as they are pretty clear on how to do this. Also my memory is not as good as the written notes!

I generally reform much more slowly and I use a limit the initial current to no more than 3mA. I will then leave the capacitor and return, say 15 minutes later, up the current again to 3mA step-by-step until the rated voltage is reached and the current reduces below 0.1mA.

I searched the internet for capacitor reforming current limits and found a wide range of values. The highest value I saw was from my Sencore LC75 manual that describes your supply setup and says to limit the current to 50 mA! I thought that value was way too high so I used 5 mA. To make it visible on the graph I multiplied the current value by 100, so 500 for the current on the graph is actually 5 mA (sorry for that confusion factor). I will try using your 3 mA value on the next caps I reform.


I assume by diectric absorption you are referring to leakage?

Until I bought and started using the LC75 I had not heard of dielectric absorption. Here is a good description that echoes what is said in the Sencore manual:
http://en.wikipedia.org/wiki/Dielectric_absorption
It goes on to say that all capacitors have some amount of this and its generally not a problem for capacitors used in power supply circuits.


The leakage current scale on the graph is too high which does not allow you to see the resultant leakage current accurately. You must be able to ascertain that the leakage is below 0.2mA in order to determine whether the capacitor is good or bad.

I was not able to find a way to show multiple scales on the graph to make it more readable. I started out using a value of .2 mA for the target final leakage value. I have since found formulas in the LC75 manual that they got from EIA RS-395. The manual provides a table of acceptable/expected leakage values calculated from those formulas. I ended up using those formulas in my program so that it calculates the target leakage value and terminates the reforming when it is reached. During the reforming process the program prints out, on the Arduino serial monitor, the voltage and current applied to the capacitor. That data is what I cut and paste into a spreadsheet to make the plots. The Arduino analog inputs have a 10 bit (0-1023) resolution so the voltage sensing resolution is 1 volt (0-1023 volts) and the current sensing resolution is .01 mA (0-10.23 mA).


The resistance indication on the graph is interesting. Perhaps the fluctuation is the dielectric rebuilding process?

The resistance shown is calculated by taking the sensed voltage and dividing by the sensed current. So it is an equivalent DC resistance due to the leakage current (not ESR). Some of the fluctuantion probably is the rebuilding process, but I suspect a good bit of it is from the limited resolution on control of the pulse width modulation used to drive the two step-up transformers shown on the schematic this thread: http://www.videokarma.org/showthread.php?t=256919
The pulse width has a range of 0 to 255 with a value of 127 producing a 50% duty cycle waveform that I use as the upper driving limit. When the leakage current gets low a single increment in the transformer drive can make a sizeable change in the quadrupled output voltage.

If you have the original RCA notes or the Rider notes, you can find how to adjust the horizontal blocking oscillator transformer without a scope.

The RCA Synchroguide oscillator circuit used by RCA and others for over a decade is quite straightforward to adjust. It comprised of the oscillator tuning adjustment and a separate sine wave stabilization coil. In the earlier sets, these were mounted on the same coil form.

In this set you are first told to short out the stabilzation coil (I believe terminals C and D) and adjust (under the chassis) to frequency. Because it is a blocking oscillator it behaves similarly to the vertical blocking oscillator in the way it locks. The best lock position for the horizontal oscillator is to sync at just the point where the sync bar just disappears to the left with this adjustment.

After adjusting the oscillator, remove the short from C and D. Turn the horizontal hold to the far left, interrupt the signal and you should find the picture out of sync. Adjust the sine coil (from outside of chassis) so that about five to seven bars are seen before it pulls into lock. The adjustments interact so that you may have to go over it a few times.

You can tell if the sine coil is misadjusted: if the sine coil is adjusted to far one way you will get double triggering and you will hear a "chipping" sound when you adjust the horizontal hold. Too far the other way and the noise immunity is lost: verticals in the picture will look coggly on weaker or noisy signals.

I do not think there is likely a resistor problem. You need to ensure the oscillator and sine wave coil are set up correctly first. I would simply leave the locking range trimmer at about 1 1/2 turn from fully clockwise and see to the oscillator first. These adjustments all interact.

Try and find the RCA notes as they are pretty clear on how to do this. Also my memory is not as good as the written notes!

If you ever get down to Buffalo, would you be willing to give me a hand with the adjustments? I'm sure you could claim some of the television booty in my basement to make it well worth your while ;)

In any event, I watched Lawrence Welk on the set last night, and for the hour that the program was on, the set was perfectly stable with a bright picture.....probably because I didn't change the channel ;)

I accidentally replaced a couple 1 kV caps with 630V caps, so I have to go back in there and do that so I'll be able to use it safely. It's shelved for the time being, figured I'd do the cap replacement at the same time as the alignment.

A lazy Sunday, so I decided to go in and replace those caps.

After that was done, I started to reassemble the set, and noticed a control that I'd missed before, because it was half-covered with a sticker.

"HORIZONTAL LINEARITY". Well son of a gun!

Powered up the set, and went to adjust it when I realized that the adjusting screw that would be IN the pot, is missing! :eek:

I have absolutely no idea how it's locking in at ALL, given that. The pot itself is slightly askew, so I'm gonna be posting in the classifieds for a horizontal linearity control, unless someone happens to read this post, and has one to spare.

I sit here scratching my head as to how it's even working, and how I missed this before!

Hi All;
Could you please give the rest of us the Value of the Horizontal Lin Pot.. Maybe, we can all go and look thru our extra spare parts or junk drawer.. (under the fridge) And see whether we have anything that will work..
THANK YOU Marty

Another interesting thing has cropped up as well. Watched the set for a bit, and I noticed that after about 15 minutes, the horizontal sweep shrunk about 1/2" on each side. The picture itself didn't seem to compress, the sweep just shrunk. It didn't shrink beyond that, but the picture did seem to dim somewhat. I can bring the picture back to the edges with the AGC, but then it goes out of focus. If I tune the set to a blank channel, it gives a full raster.....

The 6BG6 was very slightly gassy, and now it seems to be more so. Didn't check the tube yet, but I have a spare that I'm going to plunk in to see if that changes anything....

"HORIZONTAL LINEARITY". Well son of a gun!

Powered up the set, and went to adjust it when I realized that the adjusting screw that would be IN the pot, is missing! :eek:



Kamakiri,

Lets determine what happened. The Horizontal Linearity in this set is a coil and not a pot. I assume that your typing got a little ahead of your thinking.


On the apparently missing slug in horizontal linearity coil, find another slug from a junk chassis about the diameter as the hole in the present coil and try it. It probably won't be correct, but it will be a lot closer than no slug. After finding a slug and adjusting it for more or less correct horizontal linearity, repeat the horizontal alignment instructions in the sequence that RCA and Sams gives them.

http://www.earlytelevision.org/pdf/RCA-8T241-Sams-74-8.pdf

Sams page is 18, the PDF page is 21 for the alignment instructions.

Make a paper print of the page and check off each as you do it.

You will notice that Horizontal Linearity adjustment is in the 8th line of those instructions.

Misadjustemnts here could cause the shrinking that you mentioned in your next post, and so could an incorrect horiz drive setting, or a cathode resistor heating.

Consider finding a 1950's or early 60's era scope. They are not expensive. After a simple recapping, they will be as good as new. Be sure to pick one where the schematic and service instructions are available. The newer scopes are more expensive and they are not as rugged when used around tube era voltages. After you have a scope working, see how far you are out on the "peaks" that you assumed were perfect.

James.

Yes, I'd meant to say "coil", thanks for the correction :)

I've got a Hickok scope that would fit the bill, just needing a recap....something that I've been meaning to do.....actually was going to be my next project after this one.

Just so I'm following correctly, a misadjustment in this would potentially cause cathode resistor heating......is it likely that the resistors that were weak to begin with? I'm assuming the heating would cause failure, if the set were operated long enough, and the heating is being caused by an overload.

You'll need a little patience with me at this stage, as I'm trying to understand what is happening, electrically.

Just so I'm following correctly, a misadjustment in this would potentially cause cathode resistor heating......is it likely that the resistors that were weak to begin with? I'm assuming the heating would cause failure, if the set were operated long enough, and the heating is being caused by an overload.



Arrrrgghh! No. I was talking about sweep shrinkage that could be caused by misadjustment. This would be the result of the problem and not the cause.


I was also typing without thinking and changed subject in mid-sentence.



My one sentence expanded and written as three sentences:

Misadjustments in the syncro-guide circuit (page 18 above) could cause the sweep shrinking that you mentioned in your next post.

Other causes for this shrinking might be an incorrect horiz drive setting (the trim-cap), or a cathode resistor heating or one of the low voltage electrolytics in the horiz sweep. In short, anything in the horizontal sweep and sync circuits that causes a tube to pull too much current or simply a gassy tube can cause sweep shrinkage.

(Reasoning: Normally when a picture blooms, as you described, one assumes that it is a weak 1B3 or an isolating resister in the HV circuit. However, you mentioned that the image seems to be cropping while shrinking. This latter clue may or may not indicate a sync issue, especially the timing and/or pulse width, in the circuit where the horiz sync pulse is feed back to the sync tube, or simply a syncro-guide misadjustment.)
_______________________________________________

On your Hickok scope, make sure you either have the original probes, or the circuit diagrams of the original probes, so you can repair or make new ones, as they are a needed part of the scope. A set of correct probes is needed not only for use, but for the safety of your scope.

My suggestion for now is for you to go ahead and set the TV by eye. After you have repaired your scope, you recheck the sweep and set the peaks and then recheck the whole process. My guess if that you will find it works better after being scoped. These controls do interact and can sometimes confuse an experienced repairman.

For the record: During the era that these sets were in use, one would sometimes find the linearity coil slug or both the slug and brass screw missing!

Horizontal linearity has nothing to do with locking the picture. It is meant to make the picture physically more linear.. That is Not squeezed, stretched, or, oblong. It has nothing to do with the oscilator. That control is an adjustable capacitor. Looks like someone lost the screw. Hope they didn't als lose the sheet mica.
Bill Cahill

Hi All;
I am truely again amazed at the Knowledge and Insight of a number of the People in this forum..
As I have said in many other groups that I belong to, that the Knowledgeable people in the group should write a Paper or Book, so the knowledge can be passed on to those of us who are either too young or who have just gotten into that particular hobby. And so the experience and knowledge will not be lost, atfer they are gone..
It is a real education to save and print out this and many other postings that really get into the meat of a particular problem.. Thank You to those who help in the education of the rest of us..
THANK YOU Marty

Arrrrgghh! No. I was talking about sweep shrinkage that could be caused by misadjustment. This would be the result of the problem and not the cause.


I was also typing without thinking and changed subject in mid-sentence.



My one sentence expanded and written as three sentences:

Misadjustments in the syncro-guide circuit (page 18 above) could cause the sweep shrinking that you mentioned in your next post.

Other causes for this shrinking might be an incorrect horiz drive setting (the trim-cap), or a cathode resistor heating or one of the low voltage electrolytics in the horiz sweep. In short, anything in the horizontal sweep and sync circuits that causes a tube to pull too much current or simply a gassy tube can cause sweep shrinkage.

(Reasoning: Normally when a picture blooms, as you described, one assumes that it is a weak 1B3 or an isolating resister in the HV circuit. However, you mentioned that the image seems to be cropping while shrinking. This latter clue may or may not indicate a sync issue, especially the timing and/or pulse width, in the circuit where the horiz sync pulse is feed back to the sync tube, or simply a syncro-guide misadjustment.)
_______________________________________________

On your Hickok scope, make sure you either have the original probes, or the circuit diagrams of the original probes, so you can repair or make new ones, as they are a needed part of the scope. A set of correct probes is needed not only for use, but for the safety of your scope.

My suggestion for now is for you to go ahead and set the TV by eye. After you have repaired your scope, you recheck the sweep and set the peaks and then recheck the whole process. My guess if that you will find it works better after being scoped. These controls do interact and can sometimes confuse an experienced repairman.

For the record: During the era that these sets were in use, one would sometimes find the linearity coil slug or both the slug and brass screw missing!

I get where you're going here. I was going to ask, then why does the set have a full raster on blank channels, but as I'm understanding this, there wouldn't be, because there is no signal for the syncro-guide circuit to do anything *with*. Since there is a full raster off-channel, I'm not dealing with a deflection or HV issue, that would be the wrong circuit to even think about. Am I on track here?

Being responsible, the first thing I have to do is re-check all of the tubes in that section (might as well re-check them all).

Should I do any further component checks (as in resistors, etc), before I begin eyeballing the setup? The set has about 8 hours run time on it since the re-cap, I just don't want to let any "bugs" it may have do any damage.

I get where you're going here. I was going to ask, then why does the set have a full raster on blank channels, but as I'm understanding this, there wouldn't be, because there is no signal for the syncro-guide circuit to do anything *with*. Since there is a full raster off-channel, I'm not dealing with a deflection or HV issue, that would be the wrong circuit to even think about. Am I on track here?

Yes! And also why adjusting your AGC shifted this!

Many newbies mistake this for image bloom from high voltage issues and it is kinda hard to locate the trouble when looking in the wrong place.

Should I do any further component checks (as in resistors, etc), before I begin eyeballing the setup? The set has about 8 hours run time on it since the re-cap, I just don't want to let any "bugs" it may have do any damage.

As you just said, check all your tubes, but remember, the final check on a tube without any shorts is how well it works in the circuit. Actually, I usually check tubes, especially for shorts, before the first power-up, to lessen chances of frying a newly installed part.

This would be a good flow plan to complete the electrical work:

1) Check the 39 & 47 ohm resistors from the cathode of the 6BG6 to the -120v source.

(Not related to the problem at the moment, but also check to see if the fuse in the damper circuit is the correct value. I've seen some of these increased in value by servicemen to prevent callbacks as the sets got older.)

2) Find a slug that fits the horizontal linearity coil and then adjust the horizontal linearity. (Sams # L42 and Adjustment B4) Use your DVD alignment pattern for this. If your linearity does not change, your coil may be shorted, or there may be a wiring error from recapping. The set should be in its working position (not on the side) when making the final linearity adjustment.

If you think the used core you are testing makes too much change, try a smaller core.

3) At this point get yourself a red grease pencil and mark the Sams "B" numbers on the correct parts, so you won't accidentally align the wrong part. (Don't ask me how I know this is important. :dammit: )

4) If the image looks reasonably OK and only a minimum of overscan, follow the Sams page 7 for setting the AGC Threshold, but do it visually for cleanest picture (ie, back off to just before overload) for now.

5) Follow the Sams page 18 synchro-guide instructions in order, except for checking the waveform. Since you have no scope, yet, you will judge the correct position of B6 by the most stable lock-in range.

6) After finishing step 5, set the set aside for now. If it is behaving better, it is OK to temporarily slide it in the cabinet watch it, since a little running time might help to drive out any remaining moisture.

7) When you get the scope working and you have either built a low capacity probe or confirmed that yours is not leaking, check the B6 adjustment again and if it is out, correct, and let us know what you found.

After correcting the wave form, you probably will have to re-tweak some of the other adjustments.

James.

Tube test done. Geez, found more bad ones than I'd suspected. None that were "toast", but a few that were very weak. Since the set powered up on a variac when I got it to a full raster, and worked after I replaced a few capacitors, I worked the whole thing backwards and never did a complete test of the tubes till now. Dummy.

Replaced the 6BG6, and one 6SN7, listed as "Sync amp - 2nd sync sep". The 5U4 was nearly shot, and the 6AV6 tested as very marginal in one of the three tests.

Going to order some tubes, as I'm out of 5U4s and 6AV6s....on to the resistors.

After some more investigation, I encountered a newbie mistake. It seems that I didn't get the bumblebees on the first time around :rant:

Replacing the bumblebee cap on the horizontal linearity coil did the trick. It now locks in solidly when changing the channel.

Also replaced one of the two damper filter caps. The other, as it turns out, I have to order, as I must have used it for something else.

After the capacitor replacement, here's what changed....

Now, though it locks in solidly, I cannot change the horizontal hold at ALL. Nothing seems to affect it. It does lock in properly, but crank the horizontal hold to both detents, and you get no change. Same with the horizontal range control.

It also seems that I'm now getting a buzz in the audio. I can tune it out for the most part, but it's still there. At the beginning of this, I aligned the audio by ear, and got it perfect. Wonder if something is now off, now that I'm replacing components.

The high voltage is low also, as I'm getting blooming with the brightness control, and on screens that would have a very bright picture, such as all white...it goes out of focus. Still some screen shrinkage, but now only on the right side of the picture, and now the screen shrinkage is apparent off channel somewhat as well.

Now the one thing that I DID notice is that if I'm reading this correctly, some TV repairman stuck a .01 bumbebee in instead of a .05 at C91 in the sams, which is the other damper filter cap. Is this a possible cause of this stuff?

I realize that I'm not exactly following the suggestions, but as light bulbs light and I get the time, I've been working on the set with the parts I've got. I'm just going to order the cathode 6BG6 resistors on the next parts order, as it seems that I've got more work to do.....

Yep. In fact, now, if I crank the brightness, the whole picture will disappear.....

Tim, I'd have to see what you mean by picture dissappears, but, on horiz. hold control having no affect, congradulations. That's how the synchro lock works!
Bill Cahill

Okay, "picture" it this way ;)

The picture is expanding and defocusing as the brightness control is turned up. After the set has been playing for say 15 minutes or so, if I crank the brightness all the way up, the picture gets very dim, and just goes dark. I can get the picture to come back to a dim light by turning the brightness down, and I can get it back to its previous level by turning the brightness ALL the way down, then bringing it back up.

From my reading, this seems to be caused by insufficient high voltage, that the pulse from the horizontal output tube is too low, or the HV rectifier is weak or dead (which isn't the case).

I do know that this issue is worsening progressively as I replace capacitors and tubes, leading me to believe that it's the whole "weakest link" thing, and that it's all coming down to replacement of one stupid component. Once I nail that one component, I think everything will work perfectly.

If that's the way synchro lock works, well then, dammit, mine is perfect :)

Just discovered that the link above is the wrong schematic. Mine is a later production 9T246, and uses a 6W4 damper, and not a 5V4.

Sort of explains a few things. Time to go sort that out....

By the way, many thanks to Bill Cahill, for pointing out the above :)

You're welcome, Tim. Always glad to help.
Bill Cahill

Since last post, I replaced the incorrect valued cap I'd installed on the horizontal linearity coil.

Since it seems I was using the wrong Sams, I had originally put in a .01 @ 600V cap. Solid lock on horizontal. Now, I replaced the cap (C85) with a .039 @ 1 kV, and I'm back to square one with the horizontal, and being out of lock every time I change the channel.

Also replaced the .018 @ 1 kV damper filter with .02 at same rating. The bumblebee had a huge crack across the back side, which I couldn't see until removed.

Next, replaced the line filter caps (C93 & C94) with the correct stated value of .01, but upped working voltage to 630.



That said, here's my question:

Would changing the horizontal linearity coil BACK to the .01 uF from .039 cause any harm? It had solid sync lock with that cap in it, but it was wrong according to the Sams, so I switched it back in fear of causing damage.

That said, here's my question:

Would changing the horizontal linearity coil BACK to the .01 uF from .039 cause any harm? It had solid sync lock with that cap in it, but it was wrong according to the Sams, so I switched it back in fear of causing damage.

I'd switch back to the 0.01 cap. It worked for you before, and the other caps you replaced should have no effect on the horizontal hold circuit.

No. I know what's wrong.
You were loading down the poser supply before, so, horiz. osc. was right on. You changed it to correct values, taking some of the over load off, so, now, horiz. osc. needs re adjusting.
On the damper caps. not high enough voltage. They MUST be 1KV.
Tim, you are closer than you thought. The lin. coil doesn't adjust the oscilatr. Power supply was being overloaded before. Remember? Low hv?
Set was drawing more current.
Leave the correct caps in, and, re align the horiz. osc. according to instruction.
Bill Cahill

I re-read what I wrote, and went back and corrected it. I meant to say "line filter" caps, not damper filter.

No. I know what's wrong.
You were loading down the poser supply before, so, horiz. osc. was right on. You changed it to correct values, taking some of the over load off, so, now, horiz. osc. needs re adjusting.
On the damper caps. not high enough voltage. They MUST be 1KV.
Tim, you are closer than you thought. The lin. coil doesn't adjust the oscilatr. Power supply was being overloaded before. Remember? Low hv?
Set was drawing more current.
Leave the correct caps in, and, re align the horiz. osc. according to instruction.
Bill Cahill

Okay, review this with me for a sec :)

Since last update, I replaced the one .018 damper filter, which was basically split open on the back. I assume that's where I repaired the low HV issue.

I may be wrong, but I don't see how the cap on the linearity coil can affect HV. If anything, won't it affect the time base of the horizontal oscillator? In fact, when I first powered the set up, I was able to crank the control to the left and lock the picture in with multiple images.

NO. that coil isn't for adjusting the horizontal osc. frequency at all.
It makes the picture more linear. In other words, If you look at a circle on your screen, and, picture is non linear, the circle may be egg shaped, or, jagged, instead of completely round. Now, this is only a simple example, but, I hope it works.
Now, the horizontal drive will adjust the amount of voltage the control grid on the horizontal output receives. That will also affect your hv, but, not the oscilator frequency. But, if voltage is pulled down too much it can also, now, mind you, I'm not saying will, but, can affect the horizontal osc. frequency because it's loading down the horizontal output, which in turn pulls more current, which in turn pulls down power supply voltage, which will affect the frequency....

You neded to go back to the horizontal osc. coil, and, follow the directions on proper adjustment of the horizontal oscilator.
Bill Cahill

Well, for the heck of it, I tried it anyway. I took out the .018 cap and put the .01 back in. BAM! PERFECT FLAWLESS sync lock!

Picture looks great, everything is stable, sound is loud and clear, and the majority of the components in the set are new. Time to slam the hood and drive her off the lift.

Stick a fork in my 9T246, it is DONE!!!! :yippy:

Congradulations, Tim!
Like I said, the circuit was drawing more current, loading things down. You put the correct part back in, and, poof.! Problem solved..........
Bill Cahill

Actually, no, I put the wrong part back in :)

OH, boy.......... I give up........:no:
Bill Cahill

If an .008 uF capacitance difference locks in the circuit, I'm somehow good with that. Probably even less, considering a normal 20% tolerance.

This is like prof. Whopee and the 3-dimensional blackboard.

I think we all learned something here. Got 2 RCAs with this chassis but have not started yet.

Tim is the student with a good question and Bill is the professor.:yes:

Thanks Bill and Tim!

If an .008 uF capacitance difference locks in the circuit, I'm somehow good with that. Probably even less, considering a normal 20% tolerance.

While I fully understand the desire to follow the schematic "to the letter" , I understand there ARE times when this just isn't possible . Several times I have run into resonant circuits that work better with more (or less) capacitance than the circuit calls for . I had always attributed this to slight differences in components like the coils , which may themselves be slightly off of their designed tolerances .

Say for instance , your peaking coil that was supposed to be wound with 1000 turns accidentally left the factory with 950 turns instead . The capacitance required to get this particular coil to resonate at the desired frequency would certainly be different than that needed for the proper 1000 turn coil , and thus will never perfectly coincide with what the schematic calls for . It's instances like these where ya gotta give the circuit what it wants , rather than rigidly adhering to a schematic value that produces un acceptable results .

This is where a capacitor substitution box that has like 10 switchable values can aid greatly in the experimentation of finding the best fit for that particular circuit .

If an .008 uF capacitance difference locks in the circuit, I'm somehow good with that. Probably even less, considering a normal 20% tolerance.
Tim, I got lost somewhere. It first appeared that you "re-replaced" a .01 capacitor with a "correct" .039, and also replaced a .018 with a .02. Now, you have put the "incorrect" .01 back instead of the .039, nearly a 4-to-1 difference in capacitance. Are you confident that the original part you took out was a .039? Photofact schematics are not infallible, as I am sure you know. Were other adjustments or replacements made in the horizontal oscillator or output circuits, while the .01 was in place? The bottom line of it all is, if it works well now, put the cover on and enjoy it as you said.

Are you confident that the original part you took out was a .039? Photofact schematics are not infallible, as I am sure you know. Were other adjustments or replacements made in the horizontal oscillator or output circuits, while the .01 was in place?

Sam's errors, or it could be a production change at the factory that wasn't documented. Or maybe, as mentioned above, a similar but not identical replacement part was used, and that required a different cap be used to make it work. Maybe the factory ran out of the "correct" part, and made a substitution, so they could get sets built and make the production schedule, and get sets shipped out the door.

Actually, here's what happened.

Rather than read the value of the bumblebee that was on there, I went by the schematic. Schematic said it was a .01, so I put in a .01. Then, I find out that I had the wrong schematic, and the value should have been .018. It worked fine with the .01, but for accuracy's sake, I replaced it with a .018.

Turned on the set. Back to square one. Decided to go back to the .01. BAM. Dead on. One of those God moments, I guess :)

Incidentally, put another hour of runtime on it yesterday watching Family Guy and Big Bang Theory. If anything would have caused the set to overload, that woulda done it ;)

Photofact schematics are not infallible, as I am sure you know.

Ahhhh.....no, actually. I didn't know that....but I sure do now.

This set was good prep for me, because I start the DeWald in a couple weeks :)

congradulations on a job well done, Tim. As you can see, there were also changes over the life of these sets.
Bill Cahill

After just over 30 hours of play, I decided to yank the chassis and test the tubes. Replaced a weak 6J6 oscillator.

Still makes a great picture, and very stable. Have had no issues with the set :)

I'm going to hijack this thread, since my "new" 9t246 from the 2013 ETF convention
has a similar problem. This set was recapped and had several resistors replaced
by the previous owner. It basically works perfectly except for horizontal linearity,
which is abysmal. The previous owner had replaced R106 (10k) with 6.8k paralleled
with a rather large capacitor (value unknown since it was several smaller ones
paralled, values hidden in the pile). This kludge made the linearity better but
still poor. I put back in the 10k and it works, bad linearity. He also reported that he
horizontal linearity coil (I presume he meant L42) got hot. It sure appears to me that
it is not getting hot.

Presumably the first thing to do is to take a proper scope home and adjust the
waveform per Sams. Now the questions:

1) Is there a source for the proper waveforms at many places in the circuit?
(E.g. the original RCA schematic and alignments instructions.) I didn't
find one on the net.

2) Since he said the (linearity) coil got hot, maybe it had a short ... are there new ones out there, or at least experience on a proper value replacement. It looks like lots
of turns in one big solenoid. Of course maybe horizontal oscillator alignment will help
things.

3) I seem to remember reading on another forum that the two capacitors C90 and
C91 on the horizontal coil were, on some sets, not the .033 and .05 shown on Sams.
Does anybody know anything about this possibility?

4) On another subject, the input circuit to the tuner seems bizarre. L2 looks like
a balun transformer ... but its not a balun circuit. The input side, presumably 300 ohms, is not balanced, as one side is grounded? What's the idea? I'm feeding it from
either a cable box or a DVD feeding through a VCR as modulator, coax through a good balun. I get fairly large signal increase and an absolutely huge drop in impulse noise
if I ground the shield of the coax to the set chassis. I tried feeding the tuner not
through L2 but direct with 75 ohms and it worked great.

4) The set probably does not have alignment problems, and I don't have
a signal generator, so I probably won't align it. But I had an idea ... I DO have
a good spectrum analyzer. Could I feed Comcast, which has QAM on just about
every channel, flat as a pancake from 54 MHz up to 700, as a signal source and
at least check alignment with a scope probe on the spectrum analyzer? Has anybody
tried this (with AGC set so it doesn't overload.)

Other than these comments, after setting the AGC right it gives an excellent
picture of eggs lying horizontally, or plain TV shows.

Any comments very welcome.

Doug McDonald

Well, the set finally quit on me.

Turns out the issue was simple.....the picture tube was toast. I got about, oh, 60 hours of use out of that 10BP4 that was in there. The one I replaced it with, I yanked out of a locomotive that is probably best suited to parts. The tube tests pretty decently, but the picture on this set isn't as blindingly bright as the Crosley 630 clone I worked on months back.

I checked the HV to the anode (thanks to jstout for sending me that HV probe which I use ALL the time :) ), and I'm at 6 kV. Is that right for this chassis? Seems low to me.

A 10BP4 typically runs at 9kV, 6 is definitely too low.

Thought so. But I would think that if it was THAT much lower than spec, it wouldn't produce a picture at all.

It would. I recently went through a battle with low HV in a 630TS. I was getting a visible raster down around 4-5 kV as I recall. It's much brighter and sharper at 9 for sure.

So that said, where should I begin as far as a suspect component? Assuming total recap, good tubes, blah blah blah?

Adjusting the horizontal drive control should have an effect on the HV. Also, there's usually a 1Meg resistor on the HV socket in series with the HV lead to the CRT that may be bad.

Try replacing the 1B3.

The horizontal drive control seemed to have little effect. It seems just a tad brighter, but it's in the case now, so I couldn't test for HV. Gonna pull the chassis again, and go over it, as well as that resistor.

I tested the 1B3, and it was good, but I've heard that doesn't necessarily mean anything. It's an OEM tube (I think) with the "RCA Victor" script on it.....and I have plenty of NOS ones, so I'll dunk a new one in as well.

Incidentally, the set got some press today on Facebook :D

https://www.facebook.com/photo.php?fbid=10151900398058385&set=pb.281517068384.-2207520000.1377786653.&type=3&theater