Restoring a 1963 Admiral ctc-12 clone

[kramden66]

well here is the latest , going through resistors and not finding anything really bad off except for one that is 150 ohms and its 230 ohms and another that is 1k and it reads almost 2k , haven't gone through the capacitors but if they are like the ones I removed I expected to have leakage and they didn't the others may be ok too but testing will show for sure.

mike

[kramden66]

went through the capacitors in the vert horz board , they were all checking good , I almost gave up but then found a .47 with minor leakage that goes to the vertical hold control that changed my mind and the other which had a good amount of leakage was .1 in the agc section, I did find it interesting that on some when I de-soldered one leg of the cap to test it the end still connected would move a little on the board , I even found this to be true of a resistor that I never heated the pins , is it just because the solder joints are old or is it just because some weren't strong from the factory ? any ideas ?

[timmy]

oh yea the ctc12 clone how i remember, in my sears silvertone 1963, changed so many caps and it still has issues. maybe one day it will be close to perfect which these sets were never perfect but better then it is now. if its not verticle its hv and if its not all those its cant get the color just right, ahh one day . good luck with your set. those solder joints can move because the joint is old and needs to be reflowed or the foil trace has come loose from the board it self and you dont want to tear the foil otherwise you will be putting jumpers in to correct the connections of the traces that broke.

[kramden66]

there were a couple others I found , a ground to the board of the convergence was loose , a ground to board somewhere else was loose , so as I go through the set I will be checking connections , the very few terminal hand wired ones seem ok , boards were a mistake .... perhaps you just need to redo all the solder joints on yours?

mike

[kramden66]

Well I'm pretty much done going over the set , seems that the orange and brown drops are ok except for a couple I replaced , I didn't touch the if boad , I figure if theres a problem I will but left it alone , theres only one orange drop on it .
so as soon as I reconfirm that resistors I wasn't sure if they were ok or not I will give it a slow power up on the variac and then hope it works and will wonder how much adjusting may be needed as far as convergence.

what was the pin on the horizontal output tube I should measure the voltage on and what the voltage should be ? ( probably says it in the schematic )

mike

[hi_volt]

Originally Posted by kramden66

went through the capacitors in the vert horz board , they were all checking good , I almost gave up but then found a .47 with minor leakage that goes to the vertical hold control that changed my mind and the other which had a good amount of leakage was .1 in the agc section, I did find it interesting that on some when I de-soldered one leg of the cap to test it the end still connected would move a little on the board , I even found this to be true of a resistor that I never heated the pins , is it just because the solder joints are old or is it just because some weren't strong from the factory ? any ideas ?

On the old RCA chassis, it's not uncommon to get fractured solder joints. I ran into this on a Silvertone combo set I worked on a couple of months ago, which had a couple of bad connections on some jumper wires that I needed to re-solder. Fractured solder joints can be caused by either repetitive mechanical stress or by thermal cycling (typically thermal cycling in an old TV set). Bad solder joints are also common where the PC boards solder to the chassis to pick up ground. Be sure to check these as well.

[kramden66]

Well it is up and running , when slowly powered up it came to life , needs adjustments as you can see with the convergences , when it came on the picture was a blur , I tried another 1v2 and still a blur , I tried the focus and almost got a clear image but still blurred with the focus adjustment rotated as far as it would go in, so I then said what if I try the 2AV2 that was in the set to begin with - bingo a better image that focused well , odd since the tube chart and sams says 1v2 and in the set laying loose was a 1v2 admiral tube , this 2av2 doesn't even test well but seems to be working , the fly gets hot or warm , not too hot to touch , should it get warm/hot ?
there is also way too much green , tint has to pretty much go all the way to one side to get sort of normal colors , should I try the green drive or the green screen ? I can tell you the black and white image is pretty much grey that's why I'm unsure which to decrease for better tint .
is the blue issue the blue lateral or the convergence board ?
any other tips ?
the pictures show better then what can be seen in person as far as the color goes , the image is much sharper and detailed in person then the pictures show, looks like it has a clearer more detailed image then my zenith did or my friends silvertone.

thanks

[sampson159]

a good set up and your done!crt looks ok so now just to a purity and convergence procedure and enjoy.

[kramden66]

i don't recall purity tests , I will have to look it up , its on my color generator along with the dots and boxes but I don't recall what I'm supposed to do on the set , the screen or drive controls, convergence I know except it may be lateral needs adjustment too , wont know till I adjust the convergence board

[DaveWM]

check purity 1st before moving on to ANY convergence (static or dynamic).

[kramden66]

just watched a couple youtube videos on this subject, I will try to do everything without moving the yoke and see where I get , if worse comes to worse I will move the yoke to make sure red is centered and go over the whole thing again , now with the these screen adjustments I should take the weakest color and turn it up as much as it will go and then take the others and make a uniform picture closest to grey as possible correct ?

in the past when working on color sets all I had to do was minor adjustments on convergence upper right , lower left etc

mike

[Electronic M]

On the screens: turn brightness to min, flip service switch to collapse vertical to single horizontal line, turn screens down until line goes away, turn up red until a faint red line just starts to appear, turn up green until line becomes yellow, turn up blue until line becomes white, return service switch and brightness to normal then check image with color off to see if gray scale stays gray. If it is tinted adjust color drive controls for proper gray scale.

Your blue lateral is indeed off in the pics. Use the static adjustments on the convergence yoke and the blue lateral to eliminate color fringing in the center of the screen. If there is objectionable color fringing away from the center of the screen use the dynamic adjustments on the dynamic convergence circuit board to reduce them as best you can.

If the gray scale is good and the tint control does not have enough range then the drive and screen adjustments are NOT the problem; there are problems in your color demodulator that may or may not be solvable with available demodulator adjustments.

[Tubejunke]

Originally Posted by kramden66

what was the pin on the horizontal output tube I should measure the voltage on and what the voltage should be ? ( probably says it in the schematic )

mike

This is the second time in this thread that this question came up as someone explained the way that they do it, but I hope that we can get some elaboration on what I have heard is a very critical measurement on these old color sets. I don't think that you are going to measure voltage, but I may be wrong. I think that it is a current measurement. With that being said, people using "amp clamp" meters could do this much differently than those using any other meter which must be connected in series with the circuit in question. Either way, a remote way of keeping an eye on this is highly beneficial.

Also, I have read that it is a good upgrade to install a fuse in this same circuit to avoid the evident damage that can be caused by something going wrong. So, if we can get specifics on the voltage or current measurement on which section (plate, cathode, grid), as well as some ideas on a good fuse size, I think that it would help a lot of the growing crowd of vintage color TV hobbyists.

[kramden66]

I do have a rca wr-64a color bar/dot/crosshatch generator that I never used , I opened it for inspection and see a .005 dic exploded in the power section , I replaced it and its twin but the thermistor or whatever it is looks like part of it is missing so I'm not sure what the part number is and if it will work , I put it on a variac and there is oltage coming through but will let it sit overnight to help reform the electrolytics if they need to be , the one that is cardboard I should just replace anyway.
if it doesn't work I will have to use my cheaper b&k model 1230 digital i.c. color generator , it has purity , dots , crosshatch, gated rainbow and color level.

I looked on the schematic and HOT shows pin 3 and 6 at 200ma and pin 4 and 8 at 18ma 145v , pin 3 is the cathode as far as I know , so to measure the ma would be a pain without running a bunch of wires from under the chassis temporarily to measure it , but once measured if too high how do you get it down ?

[Electronic M]

In any RCA based color set it should SOP to measure HO tube cathode current(IIRC there should be a .47uF cap in parallel with the current meeter) and adjust the linearity coil for minimum cathode current. I prefer to follow the Sam's horizontal adjustment procedure, for a any given set, which usually has you adjust the horizontal oscillator for optimum performance prior to minimizing cathode current in the HO tube. It should be set to 180mA(IIRC) or lower if possible. Some roundys had a 250mA (ie. 1/4A) fuse in series with the cathode of the HO tube. IMHO it would not be a bad idea to add such a fuse mounted above the chassis...It would protect the fly from an horiz osc. failure, and allow for easy points to connect the meeter to for measuring the current.
RCA based HV systems have a tendency to blow out their flybacks from running too much current through the HO tube...Which is why replacements for RCA roundy flybacks are especially scarce compared to other flys.

You have a good flyback, Please don't waste it.