1981 19" RCA XL-100 CTC108C no brightness after CRT cleaning

[JohnCT]

Originally Posted by joe111671

Thanks Zeno. The big can on this set only has one section. I looked around for either a 4.7 or 10 mfd @350v on the board but things are pretty tight in there and I can't see the values of many of the caps so not sure which one it is.

Some had the dual section, some didn't.

IIRC, the cap in question is about the 10 o'clock position at the flyback looking from the back, but it's been many years since I did one.

In any case, you can bypass the line right at the CRT socket. Add a 10uf/350 right on kine source line to ground.

John

[joe111671]

I was determined to find this cap so I spent a little time finding the values on every electrolytic around the flyback. Picture 1 from left to right are 820@25v, 68@35v, 820@25v. Picture 2 330@35v, 30@250v. None of them are what I'm looking for except maybe the 30@250v but I don't want to assume anything.

Originally Posted by JohnCT

Some had the dual section, some didn't.

In any case, you can bypass the line right at the CRT socket. Add a 10uf/350 right on kine source line to ground.

John

John, not sure what you mean by kine source line, but my best guess is 13B which looks like it feeds R10,11,12 into Q1,2,3. I attached a picture of the back of the neck board. If you know off the top of your head where I would add the cap, I'll give it a shot. Otherwise no big deal, the picture is great as is, the bars only show up on a dark screen so I'm ok with just leaving it alone. I appreciate the input from everyone!

[zeno]

Where R1, R2 & R3 join follow that back to the main PCB. It may go through L1
first. The cap will be on that line. It will be on the cathode of a diode.
If you have a schematic of almost any solid state set the circuit will be
all but the same.

73 Zeno
LFOD !

[joe111671]

Will do. Thanks Zeno.

Originally Posted by zeno

If you have a schematic of almost any solid state set the circuit will be
all but the same.

73 Zeno
LFOD !

The only schematics I have are for my tube sets and a solid state Portacolor II but that schematic is pasted inside the back cover. I'll open it up & get a picture of it. Won't hurt to have a good picture of that as I want to see if it can be resurrected someday.

[joe111671]

Well this is turning out to be difficult to find the cap.

Zeno, when you said follow where R1, 2 & 3 join - I am assuming you were referring to R10, 11 & 12 that go to Q1, 2 & 3. So if my assumption is correct (and if it's not, then I'm way off and please correct me), the resistors are fed by wire 13B, which on the main PCB goes to 13A. 13A connects to multiple traces on the PCB that lead to various resistors, one of which leads to the video transistor that I had to replace. Trying to make a mental schematic of all that is beyond me, but I can't see where any of it is connected to the cap I'm looking for.

And the only solid state schematic I have is for that porta color (JA chassis), but on that one, the RGB transistors look to be fed off the power supply instead of the flyback, so that is no help for me with this set. That is my dilemma. Not the end of the world though, I just wanted to change the cap and see if the bars went away.

If anyone can see that I'm missing something obvious and you want to smack me, feel free to point it out.

[damen]

The Sams shows that 30 at 250 volt cap to be C117. From pin 9 of the flyback there is a diode CR112 with a small cap across it C116 that connects to a 4.7 ohm resistor R125, the resistor is probably raised above the printed board on 2 metal "stakes", then C117 is connected to the resistor and the wire run up to the CRT socket board. It then connects to the junction of R8 and R13 shown at the top of the picture you posted. Looks like it might say "9B" with L1 under it.( Sometimes the board call out numbers may be abbreviated. Example, C117 may just show C7, or CR112 may just be CR12)