Re: HELP! Altair 8800B blew smoke!
- --- In firstname.lastname@example.org, "stevenaleach"
> Capacitor C4 on a voltage regulator VR1 is fried... crispy.. charcoal..check before the next
> Also, assuming I can replace this, any suggestions of things to
> attempt?It is common for old electolytic capacitors to fail if hit with rated
voltage after long storage. The electrolytic barrier needs to be
reformed before it is put into service. This is a big problem with old
radios, TVs, etc., and the Altair should be no exception. If possible,
just replace the cap. If you want to do it the hard way, to keep
original parts, you need to 'reform' the cap.
To reform the cap, connect it to a source of variable voltage, and
slowly raise the voltage from zero (or close to it) to the working
voltage. Preferably, if you have a meter, monitor the current through
the cap to see that it doesn't get too high. Alternatively, see that
the cap doesn't start warming up. If watching the current, you should
see it rise with increased voltage, then over a span of time it will
drop off. The idea is to get up to working voltage while keeping the
current low. At working voltage, the current should eventually go to
nearly zero after a while. If not, replace the cap.