According to Bruce L. Bergman :
On Sun, 02 Oct 2005 22:45:15 GMT, "Leo Lichtman"
wrote:
"AL" wrote:

You need a buck boost transformer. A new one
will set you back $100-$150. (clip)
^^^^^^^^^^^^^^^
Maybe you could find a 32 volt transformer with sufficient current rating,
and hook the secondary up to buck line voltage.

Nice idea, but no.

When you hook a transformer up as Buck-Boost you have full primary
line voltage to ground on the secondary windings, so the transformer
you use has to be designed for it. A lot of the surplus transformers
you find are rated B-B, but the nameplate has to be readable, and you
have to dig out the spec sheets and check first.

The cheaper filament transformers that aren't rated for B-B service
will not have the proper insulation on the secondary windings for that
use, and much excitement can happen - think "Fourth Of July Finale".

It might happen the first time you plug it in, or it can wait till
after a few switching transients puncture the insulation. And best of
all it can easily turn into a fire, if you aren't standing there with
a fire extinguisher close at hand...

Well ... filament transformers -- especially those which can
handle sufficient current -- are often designed for use with high power
transmitting tubes, which often work with the filament of the tube at
a rather high DC voltage.

However 32V is more likely to be a power supply transformer, not
a filament transformer, which I agree may well not have sufficient
isolation to allow the intended application.

Enjoy,
DoN.
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