Color problem with Zenith - Videokarma.org TV - Video

hakaplan · #1 06-12-2008, 12:14 PM

I have a Zenith color tv from 1996, model SR2768S, serial: 621-42031090.

The blue is gone. I replaced the blue output transistor. No improvement. Don't know where to go now. There is an blue adjustment pot on the board near the transistor--should I mess with that? Would a pic of the board be helpful? It looks to be in good condition--all solder joints nice and no broken traces. Any ideas? Thanks very much.

andy · #2 06-12-2008, 12:23 PM

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hakaplan · #3 06-12-2008, 12:27 PM

Quote:

Originally Posted by andy

I wouldn't rule out the picture tube. Zenith CRTs from the mid 90's had serious quality problems. Did it happen suddenly, or gradually?

Hard to say. I think suddenly. Didn't watch it for a few years, then recently noticed that I didn't see blue. It may have been unknowingly on for a long time--like a month--my wife had turned off the cable box, but neglected to shut off the tv. Could that have caused it?

radiotvnut · #4 06-12-2008, 12:29 PM

The CRT would be the first thing I'd check as those Zenith CRT's from that time period are some of the worst ones ever made. They will lose emission and/or intermittently short and blow parts in the power supply and/or video output circuit.

Also, there are some driver transistors ahead of the output transistors. These are located on the main chassis. I've seen those fail due to a shorted CRT. You can replace the transistor and it may work for a week; then, the CRT will arc and blow it again.

I used to get these sets with bad CRT's from a local Zenith repair shop when they were only 2 or 3 years old. Sometimes, I'd get lucky and find an older one with a good CRT and take 2 sets and make 1. '90's era Zenith CRT's were bad with '93-'95 being the worst.

hakaplan · #5 06-12-2008, 12:35 PM

Well, short of replacing the CRT, is there any remedy that I could perform. I can solder, but I have no diagnostic knowledge with tv. Otherwise, I'll chuck it. Sad, really, because it's so nice and big and works fine otherwise.

jblmar · #6 06-12-2008, 12:36 PM

Try switching the leads to the Red and Blue transistors. If you now have Blue and no Red, the transistor or its associated components are bad.

Ron

JohnAdams · #7 06-12-2008, 05:14 PM

If you don't repair it and it has a 1298-03 crt module, I would be interested in it. The SR2786 used that module but I don't know about the SR2768.
Thanks

hakaplan · #8 06-12-2008, 10:26 PM

Quote:

Originally Posted by JohnAdams

If you don't repair it and it has a 1298-03 crt module, I would be interested in it. The SR2786 used that module but I don't know about the SR2768.
Thanks

I will check.