Prophet 5 Power Supply Question

[Sean Costello]

Hi DIYers,

I have a question for all of you knowledgeable types out there.  I recently
purchased a Sequential Circuits Prophet 5 (rev. 3.3); upon playing it in a
quiet situation (away from the sounds of the music store and band practice),
I noticed it was emitting a hum.  The hum comes from the machine itself, and
can be felt as a slight vibration in the music stand.  The output seems to
be free of this hum, so it is not a simple ground loop problem (the hum can
be heard without an amplifier).

Is this normal?  Any idea what could be causing this hum?  I presume it is
something in the power supply, but I don't know what it would be.  Is this
something that I should have serviced?  Will it cause damage to my Prophet?
Does this sound too much like a letter to Dear Abby?

Sign me...

Perplexed

(Sean Costello)