My Christmas day 9T246 restoration! Almost.....

[Zenith6S321]

Originally Posted by Geist

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

Originally Posted by Einar72

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.

[Geist]

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

[Zenith6S321]

[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.

[Zenith6S321]

Originally Posted by Geist

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.

[Geist]

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

[Sandy G]

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..

[Geist]

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

[Sandy G]

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...

[Kamakiri]

Originally Posted by earlyfilm

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/R...-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?

[Penthode]

[QUOTE=Zenith6S321;3058457]

Originally Posted by DaveWM

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?

[Penthode]

Originally Posted by Kamakiri

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!

[Zenith6S321]

Originally Posted by Penthode

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.

Originally Posted by Penthode

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.

Originally Posted by Penthode

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).

Originally Posted by Penthode

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.

[Kamakiri]

Originally Posted by Penthode

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.

[Kamakiri]

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!

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!

[Geist]

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