[GreenKeys] Dovetron Tempest Update

[Jack]

I am working on getting a Tempest Dovetron to work
with full RS232 TX and RX. It's already available, but
some options need to be set.

In the meantime, I have found that the HV loop suupply
is hiding in that unit. If you look at the power transformer you
will find a BLACK and WHITE/BROWN pair of wires that
are terminated on the PC board but are unused. These are
the 130VAC leads used in the more standard Dovetrons. 
The circuit board also has the PC lands for the bridge diodes,
a 15 ohm resistor and a HV electrolytic cap which make
up the Loop supply in the "normal" units. The only
complication would be to add suitable current limiting resistors;
they usually give off a lot of heat and you would have to be careful
where you put them. This current limiting is critical
to proper operation of your TTY and if you forget them, 
you cook the coils and that's the end of your TTY. The typical
value needed is around 5000 ohms at about 25 watts for a
60 milliampere loop current.

Jack WA2HWJ

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