[AMRadio] BC610 110v using one leg of 2207

Donald Chester k4kyv at hotmail.com
Mon Nov 6 00:11:10 EST 2006

>From: "Jim candela" <jcandela at prodigy.net>

>I am talking about a simple auto-transformer to transform 220 down to 110
>vac. Using this method you can pull power from both HOT legs of your 220,
>and not worry about whether that 3rd wire is a ground or neutral, or what
>gauge wire that wire is.

Some 3-wire cable designed for 220 volts only has a smaller neutral wire 
than the 2 hot wires.  If you are going to pull 110 off the neutral and one 
hot, you need to be sure that the 3 conductors are the same gauge.  
Otherwise, the voltage will sag under load on one side of the line while the 
voltage will increase on the opposite side.  This could damage certain 
equipment and could even be a safety hazard.  Also, make sure the 3rd wire 
really is a neutral, not just a safety ground.  The safety ground might not 
be wired directly to the neutral wire at the fuse  box with a connection 
designed to pull  the same current as the hot wires.

I have a large 220-110v stepdown Sola transformer, and it gives better 
regulation out to the exterior shack, than using one of the 110 volt 
circuits directly.  It also provides some isolation against rf crud on the 
line.  However, I am  not presently using it.

One problem I have with this method is leaving the tranformer in line 
unattended all the time.  It  could become a fire hazard in the event one of 
the windings in the transformer develops shorted turns, or the transformer 
is zapped with lightning.  I have seen the major mess that resulted from a 
power transformer burn-out in a tube-type stereo amplifier that happened to 
be left on all night.  I could imagine what would have happened if that had 
been a multi-kva transformer instead of a small power transformer.

Maybe the transformer could be mounted in a fire-proof case or metal rack 
away from flammable material, but there would still be the possibility of 
smoke damage from burnt tar and paper inside the transformer.  Transformers, 
even hermetically sealed ones, will often produce a  lot of smoke before the 
fuse blows (if there is one).

Don k4kyv

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