[Milsurplus] GP-7 transmitter

[W2HX]

5 different filament voltages?! wow. Surprising they couldn't have found tubes that shared more of a common voltage. Would have saved some transformer hardware. Ok, so if I really want one of these, I'll have to find an 800 Hz supply. hmmm

thanks
Eugene

________________________________________
From: milsurplus-bounces at mailman.qth.net <milsurplus-bounces at mailman.qth.net> on behalf of Jack Antonio <scr287 at att.net>
Sent: Thursday, February 28, 2019 12:27 PM
To: milsurplus at mailman.qth.net
Subject: Re: [Milsurplus] GP-7 transmitter

On 2/28/2019 10:48 AM, W2HX wrote:
> Silly question on my part. Other than a fan that might be expecting AC, the filaments and B+ are DC, right?
Not so silly.  The filaments are all AC driven. There is a transformer
in the unit with 5 secondaries, just for tube filaments. The B+ supplies
are DC, there is a 5Z3 and a pair of 1616 rectifiers.

I forgot about the fan, probably shouldn't rely on my memory at 4AM. As
Mike says, it is an AC fan.

> So why not create an outboard power supply to generate 2000 VDC and >whatever else it needs?

I have heard of this being done, but since the GP transmitter power
supplies are internal, the voltages are not brought out to a connector,
so getting from outside to inside will be an issue. Also, it will need
to supply 5 different filament voltages.

Rob asked about keying, the keying relay itself is DC operated,
jumperable to either 14 or 28V. However the keying relay does key the
primary AC to the high voltage transformer.

>Anyone know how many watts need to be supplied by such a supply?

The tag on the transmitter says it requires 8A of 120V. Somewhere
I've seen a tabulation of the AC power required for the various
modes, voice, and 1/4, 1/2 and Full CW, but I can't find it
right now. I believe the 8A is for full power CW.


Jack Antonio
WA7DIA
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