Date   : Tue, 20 Oct 2009 10:42:10 +0100 (WET-DST)
From   : PCOGHLAN@... (Peter Coghlan)
Subject: Dual drive power supply

> I've noticed that the power supply on my dual drives is making a bit of a
> "noise" - audible, not electrical. Best described as an oscillating hum.
>
> With the previous discussions on the Beeb Power Supplies, I wondered if this
> was a sign the capacitors on this psu were also starting to show their age
> and should be replaced. Or was it just a bad design in the first place.
>

Capacitors don't tend to make noise themselves but if they loose capacitance,
the resulting poorer smoothing could result in wound components making more
noise than they otherwise would. The wound components can also manage to
make noise all on their own without any help from the capacitors.

An oscilloscope or ESR meter would probably be required to check out the
capacitors conclusively. An isolating transformer could also be necessary
to make it possible to use the oscilloscope with certain designs of power
supply if things are not to go bang when the probes are applied.

If the noise it not excessive and the outputs from the power supply are
reasonably correct (right voltage, not too much ripple), I would leave
well enough alone.

Regards,
Peter.