Also check the bridge rectifier or the 4 diodes, don't recall what was in
there.
Maybe one or all are shorted?

Nitespark wrote:

Carl Franck wrote:
Dear NewsReaders, I have a Astron RS-20A power supply that has started
blowing its fuse even without a load. Until now it has been perfectly
reliable. I would be much obliged for any advice as to what to look
for first as I try to repair it.
Sincerely, Carl KB2KDV

Possibly a bad pass transistor. Try pulling each pass transistor out
one at a time (or pull them all out and put them back one at a time
until you blow a fuse) or if you have a transistor checker, check them.
Another possibility, is you are getting an over voltage and the
crow-bar circuit is activated. This could be caused by a problem in the
regulator circuit. Possibly a bad LM723 regulator IC. These chips are
pretty inexpensive and readily available.

Andy
WD4KDN

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