Mcintosh power amp/transformer hum...

Hoping someone might know what the answer to this problem is.

My power amp is a solid state Mcintosh, model MC 2505. There is a hum that comes from the right channel but the left always stays dead quiet. If you put your ear up to the amp you can hear the hum coming from the power transformer. This problem is intermittent, but lately is there most of the time. The only time that it went away while I was in the room listening was when I got up to flip a record, touched the preamp and got a little shock- the hum went away instantly.

Any suggestions folks?

Thanks,
Brad