View Full Version : Zenith 20BC50 flyback


andy
07-26-2016, 03:02 AM
Does anyone know if the flyback for a 21" Zenith 20BC50 is the same as the one for the 25" model? I have a 25" with an burnt flyback, and I also have a flyback I saved from a rusty 21" that I scrapped years ago. It has a lot of connections, so I would like to know before I try it. The two flybacks look slightly different (possibly made by different suppliers). I can't see any identifying numbers on the one in the set.

zeno
07-26-2016, 08:39 AM
If its the same chassis ## it probably is the same.
This is when they were changing the chassis numbering scheme
from tube count to screen size for the first numbers.
Most Zenith FBT's start with an S-##### & are
marked EIA 343 so Zenith made. They are not a quick
swap so be sure first.
I bet someone has the factory manuals & can check for you.

73 Zeno:smoke:

dieseljeep
07-26-2016, 11:31 AM
If its the same chassis ## it probably is the same.
This is when they were changing the chassis numbering scheme
from tube count to screen size for the first numbers.
Most Zenith FBT's start with an S-##### & are
marked EIA 343 so Zenith made. They are not a quick
swap so be sure first.
I bet someone has the factory manuals & can check for you.

73 Zeno:smoke:

I only worked on one of those, through the years. The flyback was bad and the Zenith distributor never stocked it, it have to be ordered from the factory.
It struck me as strange, as Zenith always had the best stocks of parts, as well as RCA.
IIRC, that was the model that wasn't very popular and one sold by the early big box stores. A real loss-leader model. :sigh:

andy
07-30-2016, 03:00 PM
The spare flyback I have is marked:S-83360. Can anyone confirm that it does go to a 25" 20BC50?

Adam
07-30-2016, 05:48 PM
The Zenith manual for the 20BC50 (CM117S2) says the flyback is a S-87813. But it doesn't give any kind of cross reference.

zeno
07-31-2016, 09:33 AM
Now you need a Zenith parts price book to see if any subs. I dont
have one.

73 Zeno:smoke:

drh4683
07-31-2016, 11:02 PM
Per my 1983 Zenith parts book, it shows that part# S-87813 was first used in 1972 models and superseded by part# 895-735 in 1976. The 895-735 was available for $65.45 back in '83.

zeno
08-01-2016, 07:05 AM
Sounds like its a kit. Gotta give them credit still having
the part when those sets were being automaticly junked.
Expensive too. FBT, probably a HOT & a few other tubes
about $175. Time for a new set.....

73 Zeno:smoke:

andy
08-01-2016, 12:06 PM
Can anyone tell me what the flyback I have goes to? I'm starting to think it's a slightly older chassis.

There's a chance the original can be saved. It looks like the problem was caused by carbon tracking on the phenolic board that the terminals and other components are mounted on. It was arcing from the HOT plate terminal to the core. There's a hole burned through the board and some damage to the primary, but the HV winding looks fine. I'm hoping the damage is confined to the edge of the insulating layers, and not the windings themselves.

dieseljeep
08-01-2016, 12:09 PM
Sounds like its a kit. Gotta give them credit still having
the part when those sets were being automaticly junked.
Expensive too. FBT, probably a HOT & a few other tubes
about $175. Time for a new set.....

73 Zeno:smoke:

IIRC, the set, I replaced the flyback in was about 5 YO. I don't remember it as a kit, just the FB and was no where that pricey.
1983 was a lot later and Zenith had a reputation for parts availability, even on their older products. Too bad, things went the way they did. :sigh:

Adam
08-01-2016, 12:32 PM
S-87813 refers to "Horizontal Sweep Transformer & Assoc. Components". It gives separate part numbers for the other components mounted to that board, but not the flyback itself.