Does anybody know what could be causing a loud pop sound once in a while with this Zenith Chromacolor II (chassis 25EC58)? It is VERY loud and the picture turns off briefly (the audio keeps going), and then the picture warms up again. My guess is the tripler or the flyback transformer is bad. I just replaced the HV tripler with an NTE replacement, and a repairman said that it could be defective (it was getting hot and causing focus issues), but it wasn't until recently when the TV kept "blowing up" and self healing itself! It doesn't happen that often, but it is serious enough to the point that I won't turn it on again until I replace something. It seems like a fire hazard to me. The HV tripler may have nothing to do with the issue, but that is what has been giving me the most trouble.

Check the Focus connector inside the CRT socket to make sure it isn't arcing over.

I had a Philco I bought used in the 70's that would pop very loudly every so often, the rebuilt CRT would go bad after a bout a month also. After the second tube was replaced I got rid of the set and told the person (a repairman) what it was doing.

He found a bad CRT socket arcing inside, it was basically stripping the Cathode of the tube a little bit each time it arced causing it to fail very quickly.

Your socket has some suspicious discoloration in the area of the Focus pin.

Thanks for the input. What does arcing mean, is there a way I can confirm that that is the problem without any testing equipment? Where do I find a new CRT socket?

Arcing, i.e. the electricity is jumping from one place to another where it shouldn't, possibly inside the socket or it could also be arcing across the dirt around the Anode connector on the CRT (i.e. the suction cup thing on the bell of the CRT) the Tripler is a common failure point on these, usually you will see a crack or some evidence of arcing such as a black discoloration from Carbon tracking where it has burned a path in the plastic.

It's not so easy to see inside the tube socket to see if it's arcing, I'd pull it off the tube and look closlely where the pins go in, look for black marks or other evidence it's arcing across, of course if it's arcing internally that's more difficult to find, if the socket comes apart that will make it a lot easier.

I noticed something about your Tripler, it was usual to have a blob of Silicone Rubber on the tops of the posts where the wires connect, I don't see any on yours, that could allow it to arc across, especially if the solder joints aren't smooth and free of sharp edges.

I would put some good Dielectric Silicone rubber on those connections and see if that fixes your problem, this is especially true if it wasn't doing this before you replaced the Tripler.

I never saw the TV work before I replaced the tripler, and I don't recall the previous owner saying anything about the noise. I remember seeing rubber on just one terminal (the large red wire connecting the flyback to the HV tripler) of the original tripler. I know that sometimes, there is clicking (not popping) coming from it and a black line flashes on the screen. This isn't a big problem, but you are probably right that silicone rubber would help. However, I did cover the terminals with some electric tape after the picture was taken, but the high voltage is probably strong enough to make it through the thin tape. I will check the CRT socket, and if that looks okay, then the loud popping is likely coming from the tripler as well.

Make sure the area where the Dag grounding wire is, is clean & the contact is good to the Dag on the CRT.
Have cleared up a lot of popping sets by doing that ez fix.

Where is the Dag Wire?

It can be a partial loop of wire, a strip or 2 of braided wire or metal fingers that ground the dag to the chassis.
Its a pressure type grounding setup.

This is a problem, it's leaking across those terminals, under certain conditions it might arc across with a loud snap.

I would Silicone the terminal and try it before I did anything else.

I used to replace those back in the day and they had Silicone on them from the factory.

The one time I got a jolt from a TV is from bumping into the tripler input terminals (the set I was working on had the tripler in a very exposed location above the back of the chassis), so getting silicone on those terminals in general is a Good Thing. As for me, no lasting harm, just a LOT of respect for the voltages that lurk inside a TV!

I got a jolt the same way. The TV popped again when I did that. It sure looks like the exposed terminals are what is causing the problem. Thanks to everybody for their advice on using silicone rubber.

One more thing. Do you think the exposed terminals could cause a continuous focus issue? The repairman noticed that the picture got lighter and darker when he turned the focus control, and I have been having some picture problems. The tripler was also getting hotter than usual. He said it was probably a defective tripler, but he said nothing about puting silicone rubber around the terminals. I was planning on buying another tripler, but after reading some of the comments, maybe this was the problem all along. What do you think?

By the way, does anyone know what brand silicone to use for this purpose? I can't tell the difference between silicone designed for electric insulators or silicone used for outdoor weather conditions. Is there a difference?

I have always used aquarium grade RTV for insulating.
The chemicals don't harm the electronics like some other types do.
Never have had a problem with using it in 20+ years now.

Possibly if it's been arcing across it might have damaged the Focus rectifiers inside the tripler, just a guess.

My guess it would be a cracked resistor arching.

Hi ghjkl67,
this sounds like a defective tripler.i might be wrong.
i remember those triplers were prone to cracks on the bottom-arcs occurred then.
since this is probably a "new old stock" part-take a good look for tiny cracks on the case.
you can use silicon to seal the cracks-not the best idea but i did seal cracked triplers for my own sets and they worked fine for years.
make sure flyback and the hv connector are clean.
you mentioned that "I know that sometimes, there is clicking (not popping) coming from it and a black line flashes on the screen."
with this problem-i discharged the crt and cleaned everything HV with alcohol including the surrounding area of the crt where the hv connected.then i dismantled the crt socket and cleaned it as well.
as mentioned before-dirty crt sockets can cause focus hv to arc.
hope this helps,
Ronl

I just bought an original Zenith tripler replacement kit. My only concern is that it is 20 years old, but if it does work, it should fix the problem and work for another 40 years.

I installed the other tripler with silicone and it didn't fix the problwm. The only difference it that the TV pops only when it is turning on. Since the sound is not random anymore, I was able to look in the back and see where the arcing is coming from. There is a small spark coming from a large exposed coil that wraps around the back of the picture tube. It is hard to see where it is arcing to, probably to one of the nearby wires. Any suggestions on insulating this coil?

Didn't those models suffer from defective caps in the horizontal output circuit that could cause the HV to go out of control (sometimes high enough to blow the neck of the CRT)? I believe the bad caps were white tubular, and the replacements were orange drops.