zenith 20bc50 problems - Videokarma.org TV - Video

daduke · #1 11-01-2012, 07:27 PM

i have a 20bc50 chassis zenith i use as my everyday tv i did a semi full recap ( didn't do lytic cans) when i got it about 2 years ago. its been working well since i started using it daily about 7 weeks ago. last night we were watching tv and it had been on maybe 4 hours and suddenly the vertical went jittery, its not interlacing correctly and its stretching the picture.

i have done nothing recently to the set except perform a full setup. i currently have no pictures of it showing the problem but i will soon ( i have no internet at home)

i do have pics of the tv from when i first got it and recapped it just to add some eye candy
http://i159.photobucket.com/albums/t...v/DSC05978.jpg
http://i159.photobucket.com/albums/t...v/DSC05953.jpg
http://i159.photobucket.com/albums/t...v/DSC05956.jpg

DaveWM · #2 11-01-2012, 07:35 PM

I would look at the electrolytic that is attached to the cathode of the vert out.
may be shorting out.

ctc17 · #3 11-01-2012, 07:49 PM

I have one of those sitting right here next to me that working perfect. All origonal not one part replaced.
If you need any info or me to check anything like voltages on it let me know.

Could be anything in the vert circuit from a bad pot to a small value cap. I think they use a VDR too that can cause issues. I would have to look at the schematic.

daduke · #4 11-02-2012, 05:38 PM

well i took it apart checked everything redid all of my solder work and cleaned the controls. it worked for a few minutes and started again then started making a weird buzzy hum and vertical would collapse and pop back. now all i can get is 3 very badly converged horizontal lines

ctc17 · #5 11-02-2012, 05:49 PM

Try a new tube first then if that doesnt work start checking dc voltages. Do you have the schematic for it?

daduke · #6 11-02-2012, 09:46 PM

i do not have the schematic also dont have another tube but ill try and get one next chance i can.

heres a pic of what its doing now
http://i159.photobucket.com/albums/t...7/DSC02317.jpg

DaveWM · #7 11-02-2012, 10:09 PM

don't leave it like that, you can damage the CRT, turn the brightness down during trouble shooting.

daduke · #8 11-02-2012, 10:21 PM

i know i just turned it up so i could take a picture

ctc17 · #9 11-02-2012, 10:39 PM

That looks like more than a vertical problem to me. The lack of width and foldover in the middle plus no convergence looks like it may be some kind of horizontal issue or power supply.

Im sure i have the schematic around here and can scan it if it would help. I have a feeling thats going to be a tough one to fix so get the vicodin out

daduke · #10 11-02-2012, 11:15 PM

thanks, a schematic would be great

it had good horizontal for awhile so im thinking its probably power supply one of those cans i didnt replace is probably starting to die .

Norbert · #11 11-05-2012, 10:16 AM

Check the vertical blanker transistor. They are known to cause all sorts of funky vertical problems.

daduke · #12 11-06-2012, 05:40 PM

I replaced some of the capacitors. horizontal seems to work and the convergence is working again. so hopefully Replacing the rest will fix my issues.

daduke · #13 01-28-2013, 06:36 PM

well i finally have internet again. I ordered the parts and replaced all the capacitors id left behind. now i have a picture its lacking height but its an improvement. still don't know where to go though without a schematic.

daduke · #14 01-28-2013, 10:58 PM

well i think i found it resistor burned up off the filters. burned right in the spot the value is so i cant read it.

Norbert · #15 01-29-2013, 08:27 AM

Those usually won't burn up on their own unless something is loading them down. They can take a hard hit and still be within reason, but seeing that you cut one of the leads, how does it ohm out? Can you specify where one of the leads is going as to track down which resistor it is. I have schematics for that chassis even though it's been years since I worked on one.