Name: Steve Kennedy
Email: steve@pacair.com
Subject: Music Man 212-HD 130
Thread: 64
Time: Fri, 27 Apr 2001 05:28:57 GMT
I suppose it is possible that the output transformer is involved, but I can think of a few things you haven't mentioned that are much more likely.
Have you tried driving a completely different cabinet and disconnect the internal speakers? Strange sympathetic harmonics can happen mechanically within an old speaker.
Also, microphonic components (especially tubes) can sympathetically vibrate and create harmonics. If it is an amplifier component, new speakers won't change a thing. If the problem goes away driving only an external set of speakers, then it is highly likely your speakers are at fault. However, if it is a vibration-induced problem, removing the "vibration generators" (speakers) from the cabinet may "hide" the problem, too.
Also, have you tried changing the power level, volume and output impedance switch? If it was an output transformer problem, I would expect a difference to occur in the manifestation of the problem when a different secondary tap is switched in.
Also, if the problem is a microphonic component, you should be able to bnump and tap all the components in the amp with a wooden stick and possibly isolate it that way.