[R-390] Question about VARIAC

[rbethman]

Bill,

I know that I was interested in "repairing" a variac.

I wasn't interested in a COMPLETE re-winding.

By the time I get the wire size, go out and buy the right size wire, 
re-wind it, and re-assemble it, I could have less expensively simply bid 
on one off THAT place, or just go to the next nearest hamfest to get 
another.

There "should" be a method to replace JUST those windings that are 
fouled up, and NOT make an extensive costly project out of it.

Bob - N0DGN

Bill Hawkins wrote:
> An AC magnetic device is designed for a specified Volts/frequency ratio,
> like 120/60 Hz = 2.
>
> 120/400 Hz is 0.3, so the core is lighter, but it will only support 60 *
> 0.3 = 18 volts at 60 Hz.
>
> If you keep the magnetic core of the variac, you must keep the same
> number of turns.
>
> The size of the wire depends on the room available for that many turns.
> A variac winding can't be layered.
>
> The power you can draw depends on the material and weight of the core.
>
> You should use the same size wire for rewinding. You can't get more
> power with heavier wire.
>
> Rewind the core first, then flatten the top of the turns with a small
> hammer, if necessary.
>
> Use a fine file to remove enamel where the brush will contact the wire.
> Polish the exposed wire with 600 grit and crocus cloth to reduce brush
> wear.
>
> Your winding should be tight so the wire doesn't move as the brush
> moves. Maybe you'll need transformer varnish to hold it in place.
>
> If there's no fuse in the circuit, the brush is most vulnerable.
>
> The rest is best learned by experience.
>
> Bill Hawkins
>
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-- 
Bob - NØDGN