Hello all,
I'm building a HB amp for 10 meters and am looking for the best solution
to a problem I've wondered about for DECADES.
Other than using a 4 conductor plug/outlet (2-120 volt, one neutral and
one ground) how should a person deal with the 120 volt neutral?
This would be a concern for the blower, small 12 volt DC power supply
and filament transformer, and maybe something else I'm overlooking as I
write this.
I know I am guilty of just taking the neutral side of a 120 volt
component to ground, but as I understand it, the ground is never
supposed to carry current, with the neutral carrying the current from
the 120 volt stuff. The ground and the neutral are connected together
at the breaker box, but are treated as different lines in the
equipment. Back in the day, I suppose taking neutral to ground was
done, as several times I've been slightly shocked by an old boat anchor
with leaky caps. Also, GFI circuits would always trip, as they should,
when that piece of equipment was turned on.
These are things I've thought of, in no particular order.
Using a 240 > 120 step down transformer and run the 120 volt things off
of that.
Neutral to chassis ground and ground, ground, ground everything
together, and to the 240 ground coming into the power supply.
Use the common connection point between two 120 volt windings, wired in
series, on the input of the HV transformer for 240 use.
Looked at a bunch of schematics and some are kinda lacking in detail.
Most either use dedicated 120 volt winding off of the secondary of
transformer, or a separate 240 volt input transformer, I'm sure the
ones lacking in detail are not doing for nefarious reasons but to keep
from cluttering up a schematic. It's combining block diagrams with
detailed schematics. I'm sure they're doing it right, otherwise, would
not get UL approval.
I seem to remember from decades ago, seeing where someone had two
resistors between the two input lines of a 240 volt input transformer
and was using that point as neutral. Would love to know how that
worked out. Short the 240 input with two resistors in series and use
the point between the two resistors as 'neutral'.
The transformer I have, and will use, is a Peter Dahl, with no 120 volt
winding, only terminals marked '0', '240', '230' and '240'. Secondary
is NOT center-tapped, so will be using a FW bridge. No joy there.
I guess I'm leaning toward a 240/120 step down transformer.
It would be much more straightforward if I was building with all new
parts from scratch. Actually, as I think of it, my DC power supply will
take either AC voltage inputs, and automatically deal with it.
Love to hear what everyone thinks, and to hear if you've ever done
anything just a wee bit 'shady', when dealing with this issue.
73 de Steve, NR4M
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