Amp Hum

I have an old adcom amp that makes a fairly loud hum when it is on. Does anyone have any suggestions to get rid of this? Thanks
Could this just be transformer noise -- i.e. mechanical hum? I just pulled out my old Adcom GFA555 (original version from the early 80's) for use as a sub amp. Works great but has a hum that's only audible when my system is off and it is dead quiet (except for the amp). It's not a major problem, since I can't hear it when listening, but I was planning on pulling the top and trying to tighten the transformer. Maybe lay a sheet of sorbothane under it?

These old amps are such work horses. Do they ever die? The only other glitch is that the power on/off switch just broke. But, as I've seen reported elsewhere on Audiogon, it broke in the "on" position. Even when they break, they work.
Sailor, given that your amp is older, I would guess that the transformer is the culprit, either de-lamination of the plates, or mounting ... but given what I have read here, I would bet the transformer is the problem. And not a problem that should case you to dump your amp either.

If you do a search in the forums on just the word "hum", you will find probably 50 different threads. Several recommendations for use of isolation pads between the transformer and mounts seems to have provided positive results for some posters. Certainly read the threads though, because external factors have been attributed to be problems as well.

My opinion, for what it's worth.
Also: Be very careful if you open up the amp. Caps etc. can hold current for long periods of time. I just recieved a suggestion from a gentleman at AA in regard to me popping open one of my amps for a look, which was: "Only use one hand at a time, this way if you do get a shock it will not travel from one hand to the other through your body" (which would be straight through the heart). I have been shocked in the past by electronics that have been unplugged for days and even weeks (I am also not very technical, so this is all that I have to offer:-).