Zenith 25DC56

[DaveWM]

Been a while as I mostly work on my classic car now, but did have an opportunity to work on one of my daily TV's. This is the Avanti set. It lost HV when I went to turn it on the other day. Zero on the HV prob. checked with a neon bulb around the fly (not sure if that would work but what the heck), nothing, set the VOM to 5000 v and check the collector of the HOT, barely anything, drop down until I get a good reading think it was 250v but not sure. So I figured at least its getting something. Hoping for and easy fix, next up is drive. I pull the H board, and wiggle all the transistors (there was no visual inspection problems, no smell btw). Pop the board in and all is well. So pretty much a wiggle the tubes fix in the SS world.

before fixing it I was looking over the schematic in the Goodman zenith book, the power for the HOT was a bit confusing. it looks like some of the high voltages are boost, but the main power for the transistor seemed to come from an arrow that only said B power. Not 128 or 114 or one of the other supplies listed from the main power supply, they all had actual voltage listed. this "B power" I could not find a source for. Not that it matters since I got it working.

[DaveWM]

https://www.youtube.com/watch?v=-NEy-GwOT9Q

[zeno]

If the transistors are still plugged in on the 9-57 solder
them in. The sockets are less reliable than the parts. Lots
of ints especially IC's. Later rebuilts had them removed.

73 Zeno
LFOD !

[JohnCT]

Originally Posted by zeno

If the transistors are still plugged in on the 9-57 solder
them in. The sockets are less reliable than the parts. Lots
of ints especially IC's. Later rebuilts had them removed.

Absolutely. I used to solder every transistor in every Zenith module, particularly the later vert chassis. Fortunately, the chassis mounted sockets were far better than those on the modules.

John