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

--
Gun Control works!!! 3 million Holocaust victims can’t be wrong.

I had two of those go out on me in a week, caused by a brown out. BOTH
cases, the bridge went bad. The brown out affected nothing else. Not the
computers still on, radios, anything - but the Astron 20As fried. I'd
definitely go for the Bridge to check. G.W.


"Mark Russo" wrote in message
...
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

--
Gun Control works!!! 3 million Holocaust victims can't be wrong.

I had two of those go out on me in a week, caused by a brown out. BOTH
cases, the bridge went bad. The brown out affected nothing else. Not the
computers still on, radios, anything - but the Astron 20As fried. I'd
definitely go for the Bridge to check. G.W.


"Mark Russo" wrote in message
...
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

--
Gun Control works!!! 3 million Holocaust victims can't be wrong.

Thanks very much G.W. and Mark, I suer appreciate the benefit of your
expeience, Carl


Ghost Writer wrote:


: I had two of those go out on me in a week, caused by a brown out. BOTH
: cases, the bridge went bad. The brown out affected nothing else. Not the
: computers still on, radios, anything - but the Astron 20As fried. I'd
: definitely go for the Bridge to check. G.W.
:
:
: "Mark Russo" wrote in message
: ...
: 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
:
: --
: Gun Control works!!! 3 million Holocaust victims can't be wrong.
:
:
:

Thanks very much G.W. and Mark, I suer appreciate the benefit of your
expeience, Carl


Ghost Writer wrote:


: I had two of those go out on me in a week, caused by a brown out. BOTH
: cases, the bridge went bad. The brown out affected nothing else. Not the
: computers still on, radios, anything - but the Astron 20As fried. I'd
: definitely go for the Bridge to check. G.W.
:
:
: "Mark Russo" wrote in message
: ...
: 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
:
: --
: Gun Control works!!! 3 million Holocaust victims can't be wrong.
:
:
:

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


Thanks again folks for all the super help and insight. I first did as
Mark, Don and Ghost Writer suggested. Sure enough, I have one of the
two bridge rectifiers shorted. I just got its replacement. I hope I
can be 1/10 as helpful to someone soon as you all you guys have been
for me. Happy New Year, Carl KB2KDV

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


Thanks again folks for all the super help and insight. I first did as
Mark, Don and Ghost Writer suggested. Sure enough, I have one of the
two bridge rectifiers shorted. I just got its replacement. I hope I
can be 1/10 as helpful to someone soon as you all you guys have been
for me. Happy New Year, Carl KB2KDV