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-   -   Transformer issue? (http://www.videokarma.org/showthread.php?t=276025)

radio nut 07-30-2023 12:27 PM

Transformer issue?
 
I recapped a Zenith 7Ao2 chassis a while back...turned the set on and it played...well. After about 20 minutes it made a loud pop noise in the speaker and quit, dead silence.I checked voltages and found zero volts on one leg of the high voltage. The other leg was very high, about double what it should have been. I thought the transformer went out. I just got to looking at it again after about a year and found a wire that the coating crumbled off and is now touching the metal chassis. Could that cause my voltage readings if it was the " correct" shorted wire? I took care of the shorted wire and was going to fire it up but I dropped the rectifier tube and don't have a back up tube.

zeno 07-30-2023 01:26 PM

You can use a pair of rectifiers for the tube. You will get more B+
so variac it. Wire may have been in bad shape & blew opened due
to a short. Carefully check for shorts before full power.
Use dim bulb or variac to test.

73 Zeno:smoke:
LFOD !

radio nut 07-30-2023 01:44 PM

Keep in mind it has been a year sonce I touched this set....i believe the b plus was 400 and some change

dieseljeep 07-31-2023 04:48 PM

Quote:

Originally Posted by radio nut (Post 3252377)
Keep in mind it has been a year sonce I touched this set....i believe the b plus was 400 and some change

That is one of the most miserable chassis to work on!
Everything is crowded and components are piled on top of each other, especially around the B- circuit. I scrapped the one had, but saved the power transformer. It's strange also, as it doesn't mount with bolts! It uses twist tabs.
The schematic shows B+ around 220 volts or so! :sigh:

dieseljeep 08-14-2023 08:55 AM

Quote:

Originally Posted by radio nut (Post 3252377)
Keep in mind it has been a year sonce I touched this set....i believe the b plus was 400 and some change

When you get back to working on the radio, if you need a transformer for it, I have the one from the chassis I scrapped. It checks out perfectly and I'll even include a good used 6X5GT. PM me if you need it!
Dave.


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