> > I am trying to put together an interface for a IC706 to use with TR. I
> > would like to be able to use one serial port for both the frequency read
> > out and keying. I am trying to use the serial port voltages to power the
> > transistors in the frequency read out part of the interface.
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I believe this has been discussed before, and the consensus is always
use a separate
power supply for accessories. Ports were never intended for use as
PSs.
This solution requires a little guts, but the simple answer is to get
a female and male mini 2 pin connector from RS. Then get a slot cover
with say, just a single LPT
port on it. Or, if you're not using the game port, use it.
Drill a hole in the slot cover to match the RS plugs, and then simply
tap one of the 5v power supply wires and wire it to the hot pin of the
plug. Make SURE you file, grind, sandpaper the top of the slot where
the screw holds it in so you'll have a good ground. Or run a separate
wire from a good ground to the ground side of the plug.
You've now got 5V waiting for you always. Now, IF all your slot covers
are filled, drill the hole between the outputs on the cover. If you
use an old LPT cover, cut the
wires off on the inside of the cover to minimize junk in the computer.
Most power supplies list the output voltage and max current on the
top.
73
Ed
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