[Amps] AL-1500 'thump'

[Per Molund]

Steve,

I had a similar experience with an Drake L7B running RTTY into a 
Carolina Windom years ago. Turned out that both the RF choke and the 
balun ferrite core had disintegrated. Maybe You could check choke or balun?

73 de LA9XKA - Per

On 2/15/2026 7:39 PM, Steve Bookout wrote:
> 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
>
>
>
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