On Sep 28, 2005, at 5:22 PM, Jim Reid wrote:
> Hi all,
>
> Ok, I have read nearly 20 earlier posts to this list about the
> amplifier;
> some seem to have exhibited a near same symptom as my newly
> acquired unit. I was among the very first Ameritron built, probably
> around 1995 or even more early. It was used very little. I bought
> it just a few weeks ago from the fellow who had it; he is "retiring"
> from ham radio and has sold/given away everything he ever had
> in his shack, shop, roof, etc. He is now 94, and not in great
> health.
>
> Anyway, I have used this amp only on 40 meters and only for
> about two weeks. One afternoon, turned the amp ON, no
> drive to it and only the power rocker tab ON.-- BAM, -- BAM!!!!
The AL-811 I inspected had an intermittent parasite at c. 95MHz. The
fix is to lower the VHF Q of the suppressors, install glitch
protection, and replace any tubes with shattered filaments.
> I instantly shut it off again, and forgot about it as I had
> a sked, so went on barefoot on 7088 kHz.
>
> Next afternoon, same time, same band and freq., powered
> up the Ameritron, and it operated just fine for an hour or so,
> putting out plenty of power and very carefully tuned and
> loaded. So presumed all was well.
>
> Next afternoon, same time, same band and freq. (nothing
> changed about any knob, etc.). Switched on the Ameritron--
> BAM and out went the meter lights; both fuses were blown.
>
> And the Standby/Operate rocker never left Standby when
> either of the "BAM" incidents happened. Near as I can get
> from the schematic in the manual, that rocker is not involved
> with whether high voltage is on the tubes or not; only seems
> to allow the transmit relay to be energized from the base
> transceiver.
>
>> From the archives here, and over on eHam reviews, it seems
> a solution has been to install Rich Measure parasite suppressor
> kit. So ordered that from him, and he sent it instantly. I have
> sent him a check for same. So have opened up the amp again
> (could see no problem at all - no burned spots, tubes appear
> fine --they are labeled RF Parts, Made in Russia-- no filaments
> laying in the bottom of the bottles, anodes not bent, no stains
> on the inside of the glass, etc.)
>
> But to install the parts Measures has sent out here, it appears
> the amp must be disemboweled! The tube sockets are nearly
> flush with the bottom of the case; can't even see grid resistors
> under there. So, somehow that sub-chassis that the sockets
> are mounted in must come out to gain access under there.
>
> Any hints on how to do that from those who have been there/
> done that?
>
> Also, Ameritron now sells a PCB for this amp which they call
> a "Parasitic PCB". Anyone know that part, how it operates,
> where in the amp, and is it a substitute more easily installed
> than the Measures suppressor stuff?? I presume this is a
> recent "add" by Ameritron to later production amplifiers
> by Ameritron. In fact this PCB part is NOT shown in the
> manual PDF which can be downloaded from the Ameritron
> web site.
>
> Been off the list for a time as I sold away my big Henry amp
> set-up. Also went back and reclaimed my original 1950
> class B call, W6KPI. Two Hawaiian calls I have had
> out here the last 14 years, AH6NB and KH7M, just
> never seemed to be very meaningful to me. So back
> I went, hi.
>
> Best and 73, Jim Reid W6KPI/KH6
>
>
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>
>
Richard L. Measures, AG6K, 805.386.3734. www.somis.org
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