Adcom GPT-450 pre-amp/turner Humming sound

[eyzhang]

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

[Robert Morein]

It is either typical of the unit, or due to a loose transformer winding or
lamination.
The defect is generally considered benign.

Options for repair are:
1. Replacement of the transformer, parts cost of around $100
2. submerging the transformer in hot shellac
3. Whacking the transformer core, to tension the lamination. Unfortunately,
this tends to magnetically harden the core a bit. It may not matter for such
a low wattage device.

Many modern designs do not switch the transformer primary. This accounts for
the continuation of the sound when it is "off".

"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
>
>
>
>