FYI, W8JI sells upgraded HD capacitor boards, upgraded HD rectifier boards, and
upgraded soft start boards for the big box Ameritrons on his ebay site. IMO
they are very well designed, assembled, tested high quality boards that I seem
to recall Tom describing as the boards that would have gone into the AL-1500
had production costs not needed to be considered. The boards have several
improvements from the originals and are relatively easy to install.
Matt
KM5VI
From: Rejean Leveille <rejva2am@gmail.com>
Sent: Monday, February 16, 2026 2:42 PM
To: maflukey@gmail.com
Cc: Steve Bookout, NR4M <steve@nr4m.com>; amps@contesting.com
Subject: Re: [Amps] AL-1500 'thump'
Hi
In the past my soft start relay got defective, also with age it may not read
the right high voltage, easy fix be replacing the Mohm resistance..
Also if the HV was near 3600 volts, there is no safety electrolytic margin at
450 volts. All equalizer resistors need to be very close values. If their color
doesn't look like new then replace them all by ordering twice (16x). to pick up
the 8x match.
Unless you have some safety experience measuring each electrolyte DC
voltage then do not do it. The diode pcb needs to be vertically locked
and insulated
Good luck
Rejean va2am
On Mon, Feb 16, 2026 at 12:52 PM <maflukey@gmail.com <mailto:maflukey@gmail.com>
> wrote:
For safety's sake, be aware the soft start and safety interlock on some of the
AL-1500s were not factory wired per the schematic.
Matt
KM5VI
-----Original Message-----
From: Steve Bookout, NR4M <steve@nr4m.com <mailto:steve@nr4m.com> >
Sent: Monday, February 16, 2026 8:48 AM
To: maflukey@gmail.com <mailto:maflukey@gmail.com>
Cc: amps@contesting.com <mailto:amps@contesting.com>
Subject: Re: [Amps] AL-1500 'thump'
Hello Matt,
I was wrong about the soft start. It IS in the AL-1500.
My mistake was I asked ‘AI’.
On the schematic, it’s obviously there (K3 and a 10 ohm R).
Steve NR4M
Sent from my iPhone
On Feb 15, 2026, at 8:45 PM, maflukey@gmail.com <mailto:maflukey@gmail.com>
wrote:
Hi Steve,
'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.<<
Did you remove the soft start relay and inrush resistor? How old are your
PS caps and are they original or upgraded?
Matt,
KM5VI
-----Original Message-----
From: Amps <amps-bounces@contesting.com
<mailto:amps-bounces@contesting.com> > On Behalf Of Steve Bookout
Sent: Sunday, February 15, 2026 12:39 PM
To: amps@contesting.com <mailto:amps@contesting.com>
Subject: [Amps] AL-1500 'thump'
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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