Start by changing the main filter capacitors in the power supply. You can
verify them with a scope across them, to see if they are actually the cause,
if you want to test them before changing them.

If you are not experienced in this type of work, you will have to give the
amp out to a service shop for this type of work. Take care for safety
issues.

--

Greetings,

Jerry Greenberg GLG Technologies GLG
=========================================
WebPage http://www.zoom-one.com
Electronics http://www.zoom-one.com/electron.htm
=========================================


"eyzhang" wrote in message
...
Dear Experts,

I have purchased a 2nd hand Adcom GTP-450 pre-amp/turner.
The unit is in excellent condtion except that produces this
constant humming sound as long as it is plugged into the outlet
(In my case, a Belkin surge protector) even when it is off.

It is not connected to any VCR/TVs. I removed all the
connections and the sound is still there. The previous
owner told me that the humming sound has always been
there since since its purchase. Its plug doesn't have
a ground pin.

Can you let me know what causes this and how it
can be fixed? Is this a well known problem for Adcom GPT-450?
Is it a good idea to power everything off (amp, preamp,cd player)
throught a master switch on the surge protector when they are
not in use?

Thank you in advance for your help! Please reply to the group
or email me at:




Best Regards,
Eugene