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/t122/duked_2007/electronics/tv/DSC05978.jpg
http://i159.photobucket.com/albums/t122/duked_2007/electronics/tv/DSC05953.jpg
http://i159.photobucket.com/albums/t122/duked_2007/electronics/tv/DSC05956.jpg

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

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.

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

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

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/t122/duked_2007/DSC02317.jpg

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

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

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

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 .

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

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.

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.
http://i159.photobucket.com/albums/t122/duked_2007/8F9CF139-339D-4F82-B198-DA170C9FD264-348-0000002352BD6931.jpg

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.http://i159.photobucket.com/albums/t122/duked_2007/23294912-D048-4C30-A632-94A1E9897387-642-0000004AA6CBA60D.jpg

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.

its dead open its off the joint where a negotive of a 47uf and the positive of a 30 uf lytics meet +to - and jumps over to a film cap that i cant off the top of my head decode the value. though i think from staring at the resistor long enough its a 470 ohm 2 watt its the only 2 watt of its value i can find in the set.

as for what pulled it down lytic went short that's what caused all the issues in the first place.
http://i159.photobucket.com/albums/t122/duked_2007/97B5157B-40AF-4AE5-8A44-EEC65376AE9D-642-000000D4669E2662.jpg

for anyone who has thos chassis and can l;ook it should be just north of the big orange drop on the right.

http://i159.photobucket.com/albums/t122/duked_2007/3957202E-BE5F-4B0B-8345-CF66E782D424-642-000000D464194EB7.jpg

...

ended up buying the sams found that the scan is so horrible i might as well have just not gotten it at all. if anyone has the original im trying to find the value of R138 . the sams is set 1197 folder 2 if anyone can help id appreciate it.

Sams 1197 folder 2 shows R138 as 470ohm 2W.

From looking at the schematic the 30mf and 40mf caps connect + to + with one end of R136 and one end of R138. The other end of R138 goes to the 390v B source. This source is from The vert centering control.

I can scan the schematic and email it to you if you like just pm me.

well replaced the resistor blew again checked all my capacitor hookups everything was fine. traced out everything and i think there's something wrong with my focus section. this kinda makes sense before the set died the focus would be out for the first 5 minutes the set was on, and would swing in and out while playing. i just figured it was moisture or something as it would crackle and hiss for that first few minutes and would stop after the focus had come back. point is there anything known for going bad in the focus sections on these televisions and would the focus affect the hv at all? since that seems to be working.

carbon deposits for HV arcing in the HV rectifier socket, and around the flyback area could cause this. Probably low high voltage causing lack of focus while it was crackleing and hissing. Also check around the damper tube socket. The damper tube plate does tie back to the 390v (b) source. I doubt the focus problem caused the burnt resistor. Check the windings of the vertical output transformer and componants in the vertical output circuit, including the 6JC5 tube and socket.

spent last hour checking everything i could i cant find my good multimeter to save my life and the backup isn't exactly up to my needs. i pulled the hv rect. took 20 minutes as it seemed glued in finally popped out taking part of the fly back board with it :/ socket is immaculate far as i can see. only sign of arcing is on a resistor that ties to the focus voltage feed to the crt. the resistor is nowhere on my schematic ( original zenith) or the one i recieved from bill (sams) though. i checked the vertical output xfrmr as far as i can tell everything seems fine. i have neither a tester or a spare tube for the 6jc5 though i can say like every tube in this set its original. not that that means much.

http://i159.photobucket.com/albums/t122/duked_2007/DC1ED689-9E29-4DA7-A54D-3209D5403E1F-269-00000013406002B7_zps61e970a1.jpg
http://i159.photobucket.com/albums/t122/duked_2007/1B7D81C7-200C-47D8-AB50-AF46141B60EE-269-000000133AF2582D_zpsef7a5dc3.jpg
http://i159.photobucket.com/albums/t122/duked_2007/DB72ACB0-4389-45B6-BA30-9FF86A175783-269-0000001338BF39F5_zpsa5918776.jpg

Take those two philips screws out and look on the back side of that tube socket. That is where arcing usually happens.

That resistor is R168 a 4.7meg 2 watt. It comes from the wiper of the focus control to the CRT pin 9. There is also a spark gap that may be located in the CRT socket. I don't remember where it is off hand.

Arcing could cause the focus problem, but not the burnt R138.

well finally found what was wrong for sure...after i took it to a shop. vertical driver transformer is bad . anyone have one kicking around id really like to get this set fixed.

numbers would probably be helpful :P they are zenith : 95-2551 stancor: vo-714c thordarson: 26s60

shes finally back from the shop they had tor replace the vertical out put transformer and rebuild half the vertical circuit. after a set up a quick and nasty convergence shes looking nice again. well as good as it can on what is all original tubes.
http://i159.photobucket.com/albums/t122/duked_2007/th_CC4A5F06-E8B4-4AB2-B7F2-7AD0FF8B4D02-5915-0000042B2FF93161_zps5f28b5ca.jpg (http://s159.photobucket.com/user/duked_2007/media/CC4A5F06-E8B4-4AB2-B7F2-7AD0FF8B4D02-5915-0000042B2FF93161_zps5f28b5ca.jpg.html)http://i159.photobucket.com/albums/t122/duked_2007/th_29C88129-14FC-4CC0-9CC7-825790437405-5915-0000042B43684A4B_zps301ecc36.jpg (http://s159.photobucket.com/user/duked_2007/media/29C88129-14FC-4CC0-9CC7-825790437405-5915-0000042B43684A4B_zps301ecc36.jpg.html)

still has problems with focus and pincushion still. focus takes about 5 minutes to come up. pincusion is wonky at best. also having issues understanding how to set the agc.

The picture looks real good.

The second picture is the movie 'Batteries Not Included' if I'm not mistaken.

Where did you ever find a TV shop ??
And one that would take it in !
We refused all tube TV's after about 1990 &
only did select ones before that. If we fixed one we
plugged it in for the customer & once it left there were NO
guaranties, period, you wouldnt listen......
Still did radios & stereos & a few vintage TV's.

73 Zeno

it is batteries not included .

a shop here in Mariette called deal tv. said family owned since 73 so i tried them.