[Amps] AL-1200 Pop/Arching, 756 Pro II failure

[Dana Roode <K6NR@ARRL.net>]

A question for those with AL-1200 repair experience --

I bought a used AL-1200 amp a few months ago - it has a low serial number, 
108, so I assume its pretty old.  I have used it in several contests and it 
has been working well.

This weekend we were using it in the California QSO party when there was a 
loud pop and an arc visible from the side venting holes, perhaps near the 
filter capacitor and rectifier boards.  The Icom 756 PRo II I was driving it 
with went south at the same time - no transmit power (received everything 
else was fine).  The Pro II is headed back to Icom for repairs.

After the pop, we left the Al-1200 powered up and there was no smoke, smell 
or other obvious signs of failure.  We switched in the backup radio, a 
IC756, but I didnt want to risk a second radio with the Amp and did not key it.

I took apart the Al-1200 and inspected it.  I found 2-3 pieces of broken 
black plastic, as if from a diode or resister.  However, when I inspected 
the rectifier and capacitor boards, I found no sign of a broken component. 
The pieces could have been from a previous failure, or who knows.

Any thoughts?  I will likely continue my inspection and check some 
components but then I guess I will power it up and try it.  However, I don't 
really want to risk another exciter.  Hopefully my TS440 is less prone to 
ESD or whatever it was that crashed the IC756 Pro II.

  Dana Roode, K6NR



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