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!

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...

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.

that is why i use aluminum chassis only in my amplifier builds...

Are you refering to a specific varnish or would your typical polyurethane varnish commonly found in hardware stores do?

One old trick to solve buzzing transformers was to heat varnish and pop the transformer in that and leve it to dry...

Buy a decent transformer?!

polyurethane varnish is good...

the amp is pushing more than 30years old, i doubt a replacement transformer can be found....

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...