Restoring a 1963 Admiral ctc-12 clone

[kramden66]

perhaps I need to turn the hv up ? the contrast level changes depending on the scene or what is in the scene , it will look normal then scene change it will wash out and go back to normal when the scene changes again , just watched an episode of bonanza , was going to take multiple pictures but attery on phone died but was able to get one of the peacock , when it fades up its washed out , you can also see a ghost and a smear that runs across the screen , when the gong goes off and it is faded up the image goes black and the ghost is not visible, the blacks are black until fade then it becomes grey and washed out , only tube not changed in the set is the video 12BY7 I think is the number , anyway anyone know whats up? not enough agc ? hv too low ?
oh yeag have to tweak the red convergence just a little but that's not the issue here , the only way it looks and acts somewhat right is if you tune it back to where there is no color and I'm pretty certain everything is uniform at this point , try if tubes even though I put nos tubes in that test ok ?

[Electronic M]

Originally Posted by Username1

Looks good ! As for the brightness and explosions, There is a lot said here about sets with and without DC restoration to the picture tube biasing. It effects light and dark pictures, where they tend to drift off where they should be.... I can't say I have seen it so you should look to someone who has seen it.... But it's an idea, and some sets without DC restoration have strange brightness issues...

Could even be HV regulation issues..

The only tube color sets I know of that lacked DC restoration were GE sets.

It is more likely that HV regulation is your problem. If the picture shrinks horizontally and or vertically (ie. blooming occurs) during the changes in scene brightness that is a dead giveaway that HV regulation is not working correctly.

[ChrisW6ATV]

As Username1 mentioned, it very much sounds like poor DC restoration to me. I have a CTC-16 with pretty good DC restoration, and a CTC-16X that is rather lousy at it. Since I cannot see any major difference between the circuits of the two sets, I have figured that it may be something that can be adjusted to work better, perhaps with just the right amount of AGC, CRT bias, and setup of the three guns. Or, maybe swapping tubes would help? This is a "someday" project for me. My CTC-16X HV regulation seems fine, for what that is worth, and its DC restoration is not very good at all.

[kramden66]

the vertical and horizontal do not change , there is no blooming with brightness or contrast turned up and down , there has to be something not working right , I don't think it was doing this previously , so I will try swapping tubes , play with the agc , I might even turn the hv up so it is 23kv instead of what it currently running 22kv , I didn't do anything with the if board except I think I checked the orange or brown drop that was on that board , since it is shielded and tougher to get to I didn't do much to like check resistors it but maybe that's where the problem is ?
is that ghost an indication of the issue ?

mike

[kramden66]

changed the 6aw8 and it made a little difference , changed the agc and it made a little difference , the 12by7 is weak , my subs are weak or have grid/gas issues , I will try a brightener but it seems like a waste since all the guns go up high on the tester , the green being the lower of the three but none show low emissions , no gas or shorts .

I put the brightener on and as I thought it made no difference , I did rebalance the screen controls and noticed something very weird , if you turn them all down it is supposed to have a dark screen , well turned all the way down I'm getting a green line no mater where I turn the control , turning it just increases the green brilliance of the green , so what I did was balanced the red blue and green and the colors are better now when they were before , another weird if I turn up the green drive I get a little more contrast in the image.

I guess I will go over the if/video board and see what I come up with , the changing isn't as bad as it was before from scene to scene , perhaps it was the agc but it still acts like dc restoration is not right and the ghost is still present , perhaps the delay line?

[Bill R]

With all three screen controls down you should not have the green line. If there is a crt bias control you may need to turn it down until the green line goes away, then adjust all the screen controls. There may also be a resistor out of tolerance in the circuits biasing the green gun. Another curious thing is the drive controls. If I remember correctly most sets only had two drive controls. You start with them at max and reduce whichever is needed to eliminate color shading in the dark areas of the picture. End result should be a B&W picture with no color shading in the light or dark portions of the picture throuought the brightness range. If with the crt bias turned down you cant get a line with the screen control, leave that control up and turn the bias up until you get the line.

[kramden66]

I've gone over the resistors , checked coils and other things , the delay line shows resistance , not sure if it is right I will hae to see if it says in the sams what it should read, only thing I found was a 56 ohm resistor that was 90 ohms , changed it even though it doesn't sound like something that was too far off, also changed a cap just to be sure , perhaps the video out tube is the cause , it is weak , a nos one is on the way, only other thing is maybe one of the capacitors that look like resistors maybe one is no good.

does anyone know what the resistance should be on the delay line ? theres nothing on the schematic and nothing in the parts list, it could cause the ghost and dc issue couldn't it ?

[Electronic M]

One way to test the delay line is to turn the color down and bypass the delay line with a wire. If the ghosting goes away with it bypassed then you've found the problem.

[kramden66]

could I bypass it by just jumping the two ends together or does one end have to be disconnected when jumping it ?

thanks for the tip

[timmy]

boy this conversation seems all to real for me as i have a 63 silvertone with the ctc12 clone and i still have simillar problems with contrast issues changing on scene changes and some ghosting and also a bar that runs across the screen and moves alittle up and down on scene changes and the back ground colors with the bar present on a dark screen is darker on the bottom of the bar and lighter on the top of the bar . so i know what your going through here as i still didnt fine out whats going on with my set. so maybe ill sit on the side lines and maybe ill learn something new here from others that know more then me, lol,lol.....

[miniman82]

I haven't read the whole thread, but it could be a luma issue. Have you replaced the bypass cap on the contrast control? It's in the cathode circuit of the 3rd video tube, if it's not working correctly it can cause the bias on that tube to drift making scenes vary in apparent intensity- reality is you've lost degeneration on that tube to some degree.

[timmy]

Originally Posted by miniman82

I haven't read the whole thread, but it could be a luma issue. Have you replaced the bypass cap on the contrast control? It's in the cathode circuit of the 3rd video tube, if it's not working correctly it can cause the bias on that tube to drift making scenes vary in apparent intensity- reality is you've lost degeneration on that tube to some degree.

would that cap possibly be a 0.1 or .22 ? or the 2- 390 caps because this may be something that is not right on my set as well.

[miniman82]

No, it's an electrolytic cap. RCA service sheet has it as C124D, so it's likely a section of a multi-section can. Scroll down here, and look at the cathode of V708.

http://boxcarcabin.com/rcaschematics.html

[timmy]

i know my eyes are getting bad but i cant seem to find v708 in that schematic, is it infact there ?

[miniman82]

It's your 3rd video tube, the 12BY7...

If you can't find it, click the link I posted and hold Ctrl while punching the minus key to shrink the page down.