[Amps] AL-1500 'thump'

[Steve Bookout]

Hello all,

Had a friend using the station this weekend, and while sitting there 
with him, while operating on 40 meters, we both heard a 'thump' or 
'thungg' from the amp while transmitting.  Happened two or three times 
or a period of a few hours.

Reminded me of the sound the current surge makes when you first turn the 
HV on in an amp.

Puzzling to me cuz if that was it, why and why now?   And, no other 
follow up issues.  I don't think a PS filter cap would 'sorta, kinda' 
short, then not and be OK.   It would only be a small part of a larger 
'event'.  (Been there; done that and still remember the pucker factor.)

Amp was being operated in a typical fashion, with resonant load, 25 
watts of drive, ~ 40 ma grid current,  +/- 1200 watts RTTY.

Dealt with many amps before, but have not heard anything like this in 
the past.  'If' it had a soft start to deal with initial current surge, 
I might think there was a problem there, but there isn't one.

Ideas?

73 Steve NR4M