> But
> have received a few email. That say they dont use the neutral wire. Just
the two
> hot wires for 220 v. It seems to me if you dont use the third wire to
chassis.
> which goes back to breaker box. If there is a short to chassis. the
breaker
> may not trip.
This issue is important enough to beat-up until it becomes clear.
They are correct in that you do not need a neutral for 240VAC operation with
the SB-220...but you still require a third connection to ground. According
to the SB-220 schematic I found below, the SB-220 only makes use of a
neutral for 120 VAC operation. In this case, the neutral is correctly used
instead of the remaining line side.
http://home.earthlink.net/~n0ss/sb-220_schematic_11x14.pdf
The bottom line is that irrespective of 240VAC or 120VAC operation, the
SB-220 correctly requires an independent, non-current bearing, ground
connection.
The problem is more apparent with the older Alpha, Henry (and purportedly
Collins) amplifiers that make use of a current-carrying common
neutral/ground when configured for 240VAC operation. These amplifiers
require four-wire service in 240 VAC operation in order to properly isolate
neutral from ground (being joined only at the distribution panel).
-Paul, W9AC
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