Re: AI - applied inginuity drive IIgs help!

[mjmahon@aol.com (Michael J. Mahon)]

Stephen Shaw writes:

>You can get an Effective Series Resistance (ESR) meter kit from Dick Smith
>Electronics in Australia. They are on the Internet. They cost about US$35
>excluding postage/carriage. I got a friend of mine who lives in Melbourne to
>bring me one. You use them for testing electrolytic capacitors in the
>IIe/II+/IIgs power supplies - the source of most switched mode power supply
>problems. I've just fixed seven Apple (assorted) power supplies in 3 1/2 hours
>including opening them up. Buy one they are good! Reference number K7204.

ESR (I thought it was EQUIVALENT Series Resistance) is exactly the critical
issue in a filter capacitor, and this is a proven effective technique for
finding a
bad cap.

But if you don't have a table full of supplies to fix, you might consider the
technician's time-honored trick for finding a bad filter cap--bridging it with
a known-good unit of equal or greater capacitance and voltage rating.

This is best done by using clip leads with the supply off (naturally), and
then turning it on and testing.  If it works with a cap bridged, then that
cap needs replacing, and you've fixed the supply.

BTW, don't forget to short the bridging capacitor after disconnecting it,
since it may pack quite a wallop!  ;-)

-michael

 Email:  mjmahon@aol.com
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