Zenith 25EC58 Ghosting Problem

[Zenith26kc20]

Also, be on the safe side and change those white capacitors in the high voltage stage. They regulate the high voltage and when enough of them fail the neck gets cracked by too much high voltage. A warning of this coming is the set develops a width problem and the turn on "crackle" gets very pronounced. Try to get the original Zenith replacements. I can't figure why the focus affects brightness, unless the control was hooked up wrong in the past or possibly the CRT socket has some corrosion on the focus pin to the spark gaps in the socket. Be careful moving the tuner assembly around. If I remember right that set uses an incandescent based optocoupler to turn on the triac in the remote circuit and age makes it fragile and the set will go dead when it fails.

[ghjkl67]

I know where the tuner is, but I am not sure where to find the AGC line. Is it on the AGC module? If I am correct, I believe it is also called the delay line. It is a large coil under the chassis. If that is what you are referring to, I checked its continuity and it tested good. It isn't an electrolytic cap, so you are probably referring to something totally different. Have you seen this symptom before? Do you think the focus control is related to this ghosting issue?

Since I probably won't be able to pinpoint an exact capacitor, is there any larger component where the capacitor is on that I can replace? I would rather replace an entire piece, but I don't know what the AGC line looks like.

Also, thanks for the advice on replacing the white caps. The television crackles a lot, even after it is started and warmed up. Quite often, there is a light snap, and a black horizontal line flashes on the screen. I don't see any width problem though.

[Zenith26kc20]

the tuner is a small silver box on the front assembly where all the tuning wheels are located. It is a bit of a bear to remove the whole assembly but the tuner may be visible without removing the entire assembly. its about 3 inches by 5 inches and has a couple of coax cables connected to it. Look at the wires going to it for a pin with a small (usually silver) electrolytic about 1/2 to 3/4 inches long to ground on the other end. I'll try to find my EC schematic tonight and look for the cap and see if I can help narrow it's location a bit better.

[ghjkl67]

I think this is the tuner, but please correct me if I am wrong. If the capacitor is on this piece, I will probably just have to replace it, rather than finding another tuner. Tuners are so hard to come by. I couldn't quite understand when you described where to find the electrolytic. Is it on the tuner itself, or somewhere else near the tuner?

[ghjkl67]

I noticed that the tuner uses an RCA plug that goes to the chassis. Would anybody recommend plugging a composite video signal directly to this terminal in the chassis? I did not try it yet because I was afraid that it would damage something or short something out. If I can bypass the tuner entirely, that would tell me if the tuner is causing the picture problem.