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Old 28th October 2012, 02:45 AM   #1
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Default Mechanical Transformer Hum

Hi All
One of my BGW 750s transformer is emitting a predominantly 240 hz hum. I`ve researched the subject however, most solutions target DC induction on the powerline, which is not the case here as another identical, albeit younger amp on the same line is dead silent.

I`m guessing some windings have loosened over the years in this non-torroid transformer and have began to vibrate.
The transformer is securely bolted in place as are the core/winding covers.

What can be done to subdue if not eliminate this source of noise?
TIA!
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Old 28th October 2012, 04:53 AM   #2
AJT is offline AJT  Philippines
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you can remove the endbells and check the center legs that could have become loose, you can wedge a small piece of wooden shims to make them tight....then you can dip the assembly in insulating varnish, air drying type is good to use...
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Old 28th October 2012, 11:52 AM   #3
DF96 is offline DF96  England
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Sometimes the chassis acts as a sounding board. Flexible mounts can help reduce noise, but ensure electrical grounding of the transformer frame is still maintained.
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Old 28th October 2012, 12:01 PM   #4
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that is why i use aluminum chassis only in my amplifier builds...
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Old 28th October 2012, 12:25 PM   #5
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Quote:
Originally Posted by Tony View Post
you can remove the endbells and check the center legs that could have become loose, you can wedge a small piece of wooden shims to make them tight....then you can dip the assembly in insulating varnish, air drying type is good to use...
Are you refering to a specific varnish or would your typical polyurethane varnish commonly found in hardware stores do?
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Old 28th October 2012, 07:40 PM   #6
amptech is offline amptech  Scotland
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One old trick to solve buzzing transformers was to heat varnish and pop the transformer in that and leve it to dry...
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Old 28th October 2012, 08:55 PM   #7
Boscoe is offline Boscoe  United Kingdom
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Buy a decent transformer?!
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I thought about it once, but then thought again.
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Old 28th October 2012, 11:01 PM   #8
AJT is offline AJT  Philippines
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Quote:
Originally Posted by Michael F View Post
Are you referring to a specific varnish or would your typical polyurethane varnish commonly found in hardware stores do?

polyurethane varnish is good...
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Old 28th October 2012, 11:03 PM   #9
AJT is offline AJT  Philippines
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Originally Posted by Boscoe View Post
Buy a decent transformer?!
the amp is pushing more than 30years old, i doubt a replacement transformer can be found....
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Old 28th October 2012, 11:13 PM   #10
amptech is offline amptech  Scotland
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Replacements can be found.. Check your transformers secondary supply voltages.. If need be you could tap an low voltage supply down via Zener resistor
Or use regs or if there is space add a small transformer to feed the preamp stages...
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