My amp project power supply has several 120v loads as well as the 240v plate
transformer.
They include a fan that draws about 100 mA, a screen supply that will take
about 350 mA,
and a filament transformer that will probably draw about 1A.
The problem is how to connect the 120v loads. One solution is to just use a
4-wire circuit
which will provide a neutral in addition to the two hot wires and ground. Then
the 120v
loads can be connected between the hot wires and the neutral.
Another option is bridging the 120V loads across the two halves of the 240V
plate
transformer's primary. I've seen this done with fans, etc. The primary acts as
an
autotransformer to provide half voltage. Then I could use a simple 3-wire
hookup.
But I wonder how far I can go with this. If I put the filament transformer
across one half
and the screen supply across the other, would the unbalanced currents cause the
voltage on
the lightly loaded side to be excessive? This is a smallish amplifier -- the
plate
transformer is about 1 kVA.
Has anybody tried this?
No, I am NOT thinking about using the ground as a neutral! If the bridging idea
is
impractical, I'll bite the bullet and put in a 4-wire circuit.
--
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/
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