Quieting a Polytone MB II hissing/mild crackling noise.

[J M Fahey]

So it narrows the search area a lot.

One of the differential input transistors might be noisy (the Enzo theory that the "actives" are much more suspect than the "passives" )

[stanleyj]

Amp is at the shop and will report back in a week or so.

[stanleyj]

The Polytone Mini Brute is back and quieter. 1 ceramic cap that was going from preamp to reverb unit in the sub board was very microphonic and replaced with a foil cap. 2 other caps were also replaced. The reverb tank looked like it was replaced at one time but was not shielded and it was picking up a bunch of noise. My tech made a shield for the tank with cardboard and shielding foil. He said the tank was magnetic. He also cut or filed the screws from the top amp handle. The screws were going right into the reverb tank. The tank is mounted directly on top under the handle.

It is now quiet compared to what it was.
Happy to get this amp working properly. It works fantastic with my hollow body archtop.

[52 Bill]

Glad to hear that you got it back and you are happy.