You do not want to ground loop the Astron 35 Amp supply. Thus, the
factory has the negative isolated from the chassis, and it should remain
so!!! Granted it is an old design, but read below to see what can
happen if you bond the negative to the chassis.
You want to use no. 12 ga. insulated twisted pair for wiring to the
transceiver, and no more length than is necessary. You may use enough
to mount the supply on the floor under the operating desk, but don't
make the pair 8 feet long or longer, for example.
Make sure the supply is remote from the transceiver by the distance to
the floor and you should not have problems if you have a proper tuner,
and use either coax or balun plus ladder line.
Most problems with RF in the shack come about from making the feedline a
multiple of a quarter wave length on a given band, or a feed mismatch at
the feedpoint of the antenna causing RF to flow on the outer
shield of coax, or feeder coupling to one side of the antenna, in the
case of wire antennas.
If you were to short the negative to the chassis of the Astron, you
would created an AC ground loop with the 3rd pin of the AC plug. That
has caused a lightning surge to travel along a feed coax shield and into
an Astron and out by the AC third pin, but it blew up several
transistors in the Astron and the LM 317 regulator. In addition, this
type of AC ground looping, caused a nearby 2m radio to take the surge as
well, and burned out the negative copper trace on the circuit board.
Too much grounding is as bad as not any. The damage I am describing was
to a club station left plugged into the AC mains during a thunderstorm.
As Jerry says, the paralleling of transistors means if one goes, the
others can fail under the next load.
-Stuart Rohre
K5KVH
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