[TMC] Pal 350/500

[Nick England]

Welcome aboard, Chris.
Nick K4NYW

On Tue, Jul 20, 2021 at 7:46 PM Chris Bolkan <bolkyboats at gmail.com> wrote:

> First, Thank you Nick England for getting me on this site and being
> able to post!
>
> Hello! I am new to the list but not new to the admiration of TMC gear.
> I used to stare at the TMC pages in the back of the ARRL handbook
> catalog sections when I was a kid and wish I could have something like
> that. Everything else in those pages paled in comparison. It was the
> favorite equipment I wished I had and those pictures burned an image
> in my brain that will never go away.
>
> Over the years I have acquired a straight GPR90 and an RXD which I
> have used, held onto and displayed with great pride! Recently I
> acquired a PAL350 amp and PAL500 power supply with interconnecting
> cable. I am in the process of checking everything out, getting
> acquainted, fixing the little things that were not right and starting
> to power it up.
>
> To that end I have read every post in the archives of this list and
> printed out everything that I think will be helpful in getting it up
> and running properly.
>
> My first question has to do with the operation of these amps. I have
> printed out schematics of the three 350 variants and the two 500
> variants from the History site plus the instructions and addendums.
> Studying these it appears that there are two (maybe 3) ways to "KEY"
> these amplifiers.
> First would be to turn the (HV) power supply on and off with the
> "remote" relay circuit every time I want to key up, but I find that
> idea unacceptable for obvious reasons, so I don't think that is the
> way TMC intended them to be operated.
> The second way I can imagine using it is to key the amp on (output
> tubes biased to transmit) and have it resting in the biased on
> position the whole time it is turned on ready to receive a signal from
> the exciter to amplify. Is this how these amps were used with TMC
> exciters? (which I do not have)
> The third way to key the amp appears to have actually been an option
> on one of the 500 variants, which was to use a remote keying signal to
> change the bias of the output tubes from operate to cut off and back.
> This seems to me to be the most logical way to do it. That way the amp
> isn't keyed on 100% of the time, more like conventional amps I am
> familiar with are operated.
>
> One concern to me is that the PAL 500 variant that appears to have
> been sold this way seems to have an addenda to have the user reverse
> this functionality bringing it back to the grids always being biased
> on, removing the provision to bias them off from the remote relay in
> the power supply.
>
> Any help and guidance is greatly appreciated.
>
> Thank you so much! I am sure more questions are to come and I hope you
> all have patience with me.
>
> Chris Bolkan
> KI7NXY
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-- 
Nick England K4NYW
www.navy-radio.com