WOPL 400 Linda Linda

[laatsch55]

I've had a few turn to hummers on me. I would turn em on and start tightening the bolts till they quit...

 

[Gepetto]

Well I think I found the source of the excessive hum. Tapping around the plates I found a few other spots that sound hollow. Has anyone repaired something like this? First thought is using electrically insulating varnish or lacquer to fill the space and adhere the loose bit of plate together. Maybe two part epoxy?
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Any of those solutions will work for you. There is an insulating varnish on each layer of the E-I laminates anyway for eddy current reduction purposes so there is no downside. Make sure the bobbin is secure as well. Often the hum is because the bobbin core became unattached from the transformer E-I core and vibrates.

 

[girbob75]

Any of those solutions will work for you. There is an insulating varnish on each layer of the E-I laminates anyway for eddy current reduction purposes so there is no downside. Make sure the bobbin is secure as well. Often the hum is because the bobbin core became unattached from the transformer E-I core and vibrates.

I have some MG Chemicals 4226A clear on the way. Just checked the bobbin and that seems good, thanks for the tip. It's a good time to isolate the transformer from the chassis. Obtained some stainless bolts and nylon washers. I'll be using a layer of Kapton tape for the pass through.