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Old 4th April 2009, 02:06 AM   #1
pjanda1 is offline pjanda1  United States
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Default Dampen transformer endbells?

It sounds as if my transformer buzz (mechanical) may not be DC on the line. As I mentioned in the other post, most transformers make a bit of noise for me. The quietest one is an old Sherwood. I pulled the endbells off it once, and they were filled with some sort of white compound. (It was a pain to put the broken pieces back in!) In contrast, the transformer that is now giving me problems has thin endbells that actually ring like bells!

I've seen several posts about potting transformers, but wouldn't filling the endbells with something be a more gentle approach? It would inhibit cooling, but surely not to the extent that potting a transformer would, as the edges of the lams could still breath. So, what if one jammed the endbells full of something like duct seal? It is non-conductive and pretty tolerant of heat, right? If the transformer ran too hot, it would also be easy to remove.

thoughts?

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Old 4th April 2009, 06:19 AM   #2
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Does your problem disappear if you remove the endbells? If not, filling them with a compund will proably not help.
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Old 4th April 2009, 06:48 AM   #3
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Default my thoughts are

you are trying to compensate for a fault in the transformer. My background is in automotive electrical engineering. Buzzing inductors typically had a short in a winding. I'd be thoroughly testing the transformers electrical performance before I stuffed it full of anything.
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Old 4th April 2009, 02:30 PM   #4
kuroguy is offline kuroguy  United States
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I had a Hammond power transformer with a buzzing end bell. It was really annoying. If I touched the end bell the buzzing went away. In the end, I remover the end bell, poured some 2 part epoxy into the end bell and when the epoxy had set up I reassembled the transformer. No more buzzing.
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Old 4th April 2009, 02:38 PM   #5
pjanda1 is offline pjanda1  United States
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Every tube amp transformer that has been in this house has buzzed, except for one. And it was potted. Hopefully they weren't all faulty! This one just buzzes a bit louder than others. I don't know that I can "thoroughly test" it's electrical performance. It seems to behave fine. The longest I let it run under load was half an hour or so, and it didn't get very warm. I figure if it were saturating or had real troubles, it'd run hot, right?

I'll play with it some more today. I won't make any drastic moves. Epoxy putty also comes to mind.

pj
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Old 4th April 2009, 03:40 PM   #6
kuroguy is offline kuroguy  United States
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something liquid will self level and you can get a uniform layer on the inside of the bell. I also used a sanding drum on my dremel to roughen up the inside of the bell so the epoxy would adhere better.
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Old 4th April 2009, 08:28 PM   #7
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I wonder if using some of that canned expanding foam on the inside of the end shell. The kind that is used for filling gaps when installing new windows and such. It comes in at least two expansion rates. Medium and high. Perhaps the medium would work ok.
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Old 4th April 2009, 09:20 PM   #8
pjanda1 is offline pjanda1  United States
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Interesting thought! I love that stuff. I suppose the ultimate would be gorilla glue or polyurethane construction adhesive, as both expand (the former more than the latter). That certainly is a point of no return.

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Old 5th April 2009, 12:02 AM   #9
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Default Re: Dampen transformer endbells?

Quote:
Originally posted by pjanda1
I've seen several posts about potting transformers, but wouldn't filling the endbells with something be a more gentle approach?
You mean this thread? Annoying high frequency ringing from my 832 tube amp
My Hammond PT still buzzes but the ringing is gone after lining the inside of bell with fiberglass resin.
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Old 5th April 2009, 02:06 AM   #10
Jeb-D. is offline Jeb-D.  United States
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It's probably only a good idea too fill the endbells if you can use the same type of compound they use to pot transformers.

The material should have a high dielectric strength and be a good thermal conductor. Maybe if your transformer runs cool, you can get away with using something else. Unfortunately, a buzzing transformer is usually a hot transformer.

Lining the endbells probably wouldn't be a problem, but may not help that much.

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