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[TenTec] Power Supply - Hercules

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Subject: [TenTec] Power Supply - Hercules
From: geraldj@ames.net (Dr. Gerald N. Johnson, P.E.)
Date: Thu, 25 Jun 1998 09:08:34 -0500
That amp is tough service for Astrons or battery. I'm NOT a fan of
Astron power supplies. They tend to use old (1970s) technology (723
regulator chip) that's not as effective as more modern regulator in
current limiting and control and then they use it badly. It has no
thermal shut down and that leads to the gradual loss of pass transistors
until the all fry. Sometimes that hints that the emitter resistors that
should be forcing current sharing are too small. The unregulated voltage
is high enough to fry the radio when the pass transistors short so they
have to use a crowbar.

A battery spews free hydrogen and oxygen on high current loads as well
as when overcharged. The ratio of H and O is perfect stoichemetric
mixture for the best bang (though hydrogen will burn over a very wide
range of mixtures) when ignited. And these gasses tend to be wet with
sulfuric acid that eats stuff. You don't want these fumes in the house
or around the radios or even around the batteries.

A battery has to be a deep cycle (therefore not sealed) and for the amp
as large a one as you can move, preferably a couple. Any power amp's
supply voltage has a big effect on the output. Often dropping from 13.8
to 13 cuts the output by 30%. A battery will require regular
maintenance, at least monthly filling with distilled water, and regular
cleaning of the posts. Battery acid spilled will eat through jeans
(doesn't discriminate between good and bad) in seconds, and do the same
to carpet.

A fairly large deep cycle marine battery will be rated at probably 100
ampere hours. That's two hours at 50 amps... Two hours talking time.
With listening half the time and the intermittency of speech, probably
stretch to 5 hours. Then the charger has to be that big to bring it back
in 2 hours... Big chargers that don't wreck the batteries cost lost

If I didn't build my own high efficiency FET regulated supply, I think
I'd lean towards the Tentec supply as its quality ought to be better
than Astrons and you don't have the current sharing problems of
independently regulated supplies.

73, Jerry, K0CQ

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