Just a quick question. I have a Kenwood KR-3130 tuner amp. It works fine, powers on fine, but after about 15 minutes of operation the power transformer will making a buzzing noise, not coming from the speakers but coming from the transformer itself. It continues to work just fine despite the small bit of noise. Is there anything in danger here? Thanks.

No, but if it has screws with nuts you can try tightening the nuts.

Thank you! I'll check it out when I get a bit of time.

+1 for simply tightening some bolts/nuts...

Sometimes, I've needed a more extreme solution. First, LOOSEN the bolts/nuts that hold the laminations together. You may then find that the stack expands a bit--i.e. lots of gaps open up. For these cases, I get the stack loosened up as much as possible with damaging the windings. Then, douse with shellac and immediately tighten the bolts.

But---another possibility is that the winding assembly is loose on the center pole of the lamination stack. In these cases, you need to insert some kind of tapered shim.