I've had the same problem with my RS35M.
The regulator chip in mine is an LM723 chip.
I've had to replace it around 6 times over 12 years.
I'm not sure that spikes are taking it out. I think it's a matter of pass
transistor emitter/base current and the maximum current rating of the 723
series regulator. I think that their design was pushing the 723 to its limit.
I finally found a 723 brand that seems a bit more rugged (don't remember which)
and haven't had a recurrance in three years. BTW, I did check the pass
transistors
for leakage, etc and found no problems.
It took around 4 years for the original chip to fail.
I suspect that some original 723's were more rugged and so the supplies in
which they
were installed never failed.
Doug/WA1TUT
To: <tentec@contesting.com>
Date: Wed, 17 Jul 2002 19:54:25 -0700
From: Clark Savage Turner <csturner@slonet.org>
To: tentec@contesting.com
Subject: [TenTec] astron blows regulators
Curious, I have an RS-35M that keeps blowing the regulator, but it does
it after some time of operation....like a day, sometimes a few weeks,
then it goes out, supply shuts down. At first I suspected the little
regulator voltage pot, it is cheap, so I shot it with DeOxit and wiggled
it, put a new regulator in (the thing is socketed from the last owner, I
suppose this has been happening for some time!) - it worked for a couple
of weeks, powering transmit / receive cycles just fine.
There isn't much on the board, I can't see what could be killing the
regulator in there. I will replace the pot just for good measure (it
acted dirty when I set the voltage), but does anyone have any other
suggestions? Ever see this problem?
Clark
WA3JPG
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