[Amps] AL-1500 'thump'

[Aleksandar Petkovic]

I wasn't aware of his ebay store. Can you provide a link please?

Yes, I have his filter board and the EBM Papst blower in my AL-1500, but 
I bought them directly from him. I would like to see the ebay store.

73, Alek VK6APK

On 17/02/2026 12:07 pm, maflukey at gmail.com wrote:
> 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 at gmail.com>
> Sent: Monday, February 16, 2026 2:42 PM
> To: maflukey at gmail.com
> Cc: Steve Bookout, NR4M <steve at nr4m.com>; amps at 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 at gmail.com <mailto:maflukey at 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 at nr4m.com <mailto:steve at nr4m.com> >
> Sent: Monday, February 16, 2026 8:48 AM
> To: maflukey at gmail.com <mailto:maflukey at gmail.com>
> Cc: amps at contesting.com <mailto:amps at 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 at gmail.com <mailto:maflukey at 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 at contesting.com <mailto:amps-bounces at contesting.com> > On Behalf Of Steve Bookout
>> Sent: Sunday, February 15, 2026 12:39 PM
>> To: amps at contesting.com <mailto:amps at 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
>>
>>
>>
>> _______________________________________________
>> Amps mailing list
>> Amps at contesting.com <mailto:Amps at contesting.com>
>> http://lists.contesting.com/mailman/listinfo/amps
>>
>
>
> _______________________________________________
> Amps mailing list
> Amps at contesting.com <mailto:Amps at contesting.com>
> http://lists.contesting.com/mailman/listinfo/amps
>
>
>
>
>   
>