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Re: [Amps] AL-1500 'thump'

To: amps@contesting.com
Subject: Re: [Amps] AL-1500 'thump'
From: Per Molund via Amps <amps@contesting.com>
Reply-to: Per Molund <pmolund@online.no>
Date: Mon, 16 Feb 2026 22:30:34 +0100
List-post: <mailto:amps@contesting.com>
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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