[Amps] Alpha 76 question

MU 4CX250B 4cx250b at miamioh.edu
Tue Nov 24 11:51:55 EST 2015


I have an Alpha 76 that I converted to 6 m years ago, which exhibited
the same symptoms. The problem was internal arcing in one of the
elderly electrolytic capacitors in the power supply. I ended up
swapping all the capacitors and the problem has never recovered. Even
if the sparking turns out to be coming from something else, it's
probably a good idea to change the capacitors anyway. While you're at
it, clean out all the accumulated dust on the tune capacitor plates.
73,
Jim w8zr

Sent from my iPhone

> On Nov 24, 2015, at 7:39 AM, Manfred Mornhinweg <manfred at ludens.cl> wrote:
>
> Ted,
>
> > My Alpha 76 periodically "snaps" loudly (arcs?) when idling...maybe
> > every 20-30 minutes.  Any ideas what this may be?
>
> I don't know anything specific about that Alpha, but I have seen this kind of arcing at regular intervals when there is a simple power supply that has no bleeder and no load on it. There are very often lots of very narrow but tall spikes riding on the power line. When there is no load at all on a power supply, these will slowly charge the filter capacitor to such an overvoltage that something arcs.
>
> So I would suggest to check all bleeder resistors, first of all.
>
> Manfred
>
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