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Replacing a transformer in a old Zenith

John Carr

John Carr

Active Member
I am have an old cabinet unit Zenith that started smoking from the transformer pictured. 1000018782.jpg
The stereo model: SFF2535M
Transformer: T2
1000018784.jpg

Is there a good place to buy a replacement or am I going to have to make due with not exact parts that are more universal?

Any info is great, thanks.

-John Carr
1000018783.jpg
 
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Hi there, what is smoking is called the speaker output transformer.

To make positive sure, just remove tube V10 EL84 and this will cut off all B+ to that transformer. This is a fairly rare occurrence but does happen. Thank goodness it is not the big black power transformer.

Power transformers are a little harder to come by but the output transformer can probably be easily had by doing a few page scrolls on e-bay. Just type "Zenith EL84 stereo single ended tube amplifier" and you should find something.

As a matter of fact, Here ya go: No Affiliation!

www.ebay.com

Zenith Model 3F32 Stereo Tube Amplifier | eBay

Listed is a Zenith 3F32 stereo tube amplifier. Untested. Comes with 1 5U4GB rectifier and 2 EL84 tubes Russian 6P14P. As found condition. Likely needs rebuilding.<br>
www.ebay.com
 
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has to be something else wrong causing that. Only fault in the transformer itself that might do this is a short to ground on the primary side. Ohm meter will tell you. If its not shorted, look elsewhere
 
I was just typing possible causes but Gadget beat me to it. :thumbsup:

I was also going to mention the output EL84 tube being another possibility.
Either way, tube or transformer can easily be had. :beerchug:

You probably want to replace both anyway. It could have redplated and stressed the tube. The transformer windings may have shorts between windings making the red paint cook off a little making it unstable and untrustworthy to re use.

Senior moment: What is that red cover paint like stuff called again?
 
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Don't mean to hijack this thread, but I have a similar appearing amp that is a 3G32. Anyone have a legible schematic for this? Thanks, Bill
 
wlgrant6 said:
Don't mean to hijack this thread, but I have a similar appearing amp that is a 3G32. Anyone have a legible schematic for this? Thanks, Bill
Click to expand...
You can download it here, it is the same according to an e-bay Sams auction

SFF2535-1 Ch= 9G26 Radio Zenith Radio Corp.; Chicago, IL, build |Radiomuseum.org

SFF2535-1 Ch= 9G26 Radio Zenith Radio Corp.; Chicago, IL, build 1961 ?, 5 pictures, 1 schematics, 9 tubes, United States of America , semiconductors
www.radiomuseum.org www.radiomuseum.org
 
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But the radio museum link has the amp Edit: I screwed up, it does not...
There is a full sams on the auction site that has it.. , I will look more
 
century tek said:
Hi there, what is smoking is called the speaker output transformer.

To make positive sure, just remove tube V10 EL84 and this will cut off all B+ to that transformer. This is a fairly rare occurrence but does happen. Thank goodness it is not the big black power transformer.

Power transformers are a little harder to come by but the output transformer can probably be easily had by doing a few page scrolls on e-bay. Just type "Zenith EL84 stereo single ended tube amplifier" and you should find something.

As a matter of fact, Here ya go: No Affiliation!

www.ebay.com

Zenith Model 3F32 Stereo Tube Amplifier | eBay

Listed is a Zenith 3F32 stereo tube amplifier. Untested. Comes with 1 5U4GB rectifier and 2 EL84 tubes Russian 6P14P. As found condition. Likely needs rebuilding.<br>
www.ebay.com
Click to expand...
Not a fan of the "likely needs rebuildng", but definitely worth considering.
 
If this has original coupling and/or filter caps, they are quite likely bad. Looks like a single ended design, but it looks like extra wires on the primary. Guessing its going to be one of those "hum bucker" deals where the HV supply comes in to the middle of the transformer, one end to plate, and the other end to screen. Sometimes other filter caps are tied off that screen end to feed tubes upstream. If the cap to ground is bad it will flow too much current and let the smoke out. Same if the coupling cap on the output tube is bad, the tube runs too hard and flows too much current.

Its possible the output transformer survived this but an ohm check ought to confirm. Even if it is bad though, if whatever caused it to let the magic smoke out isn't fixed, its just going to happen again.
 
I agree 100% that you should replace both. Check out Antique Electronic Supply online, they probably have something that will match the specs of the old one . They have a great selection of Hammond trannes
 
Those output transformers are very specific to that amp and are two different part #s. They're using part of the primary as chokes for the B+ filtering and I can't make heads or tails of what's going on with the secondary side. Hopefully it's not toasted.

1723654609451.png

1723654563740.png
 
looks like one of those goofy mono/stereo amps that runs push-pull for mono signals and single ended for stereo.

yeah those aren't "normal" by any stretch. Other than original replacements, nothing else is going to work like this is meant to work.

but it does indeed use them as chokes, so if that second cap connected to "B" shorts, it'll make the magic smoke leak out. If not much has come out it may still be fine. I've bubbled transformers and chokes before without killing them.
 
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