RE: Humming amps :(

["Keith Doxey" <ukha@xxxxxxx>]

Change the PSU capacitors :-)

Its quite a common failing with age.

I once serviced a Citronic PPX450 ( 2 x 225W ) where the capacitors had
dried up so much due to prolonged heat and heavy use that as I used a
paintbrush to sweep the accumulated dust off the various bits in the amp,
the solder terminal on top of the capacitor actually fell off!!!

Two caps later and it was as good as new pumping out the bass.

I also decided to prevent it happening again adding some more speakers and
a
BK Electronics MXF900 :-)

Now it REALLY kicks :-)

Keith

www.diyha.co.uk
www.kat5.tv


> -----Original Message-----
> From: Tony Butler [mailto:lists@xxxxxxx]
> Sent: 12 July 2003 10:44
> To: ukha_d@xxxxxxx
> Subject: RE: [ukha_d] Humming amps :(
>
>
> > Hi Tony,
> >
> > It sounds as if the PSU smoothing capacitors have dried up
> > with threee years of cooking.
>
> DOH! And one of my projects this w/e was to add a couple of
> little fans
> to cool the cupboard :(
>
> > Is the hum still present if the ONLY thing physically
> > connected to the amp is the speaker?
>
> Yes.
>
> > If its OK with only the speakers connected but hums as soon
> > as an input is connected then somehow you have created a
> ground loop.
>
> Don't see how - I haven't touched that side of things in ages...
> I swapped the amp with the good one and it was still the same, so it's
> deffo the amp.
>
> Strange that this should happen after one definite on with no
> input (and
> hence probably volume up v.v.high) and another suspected such
> incident....
>
> Now.....how do I fix it? :/
>
> T.
>
>
>
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