[sdiy] transformers and power supplies, etc... for newbie

[Roy J. Tellason]

On Saturday 05 February 2005 03:07 pm, Tim J wrote:
> Ok, so I need to learn a bit about transformers and power supplies.  Anyone
> know of any good online resources?
>
> I recently bought acquired an old korg micropreset synth.  Its in perfect
> shape (even came with a hard shell case).  Unfortunately its 220v and I'm
> in the US.  The fuse was also missing when I got it.  To get her running I
> guess I need a step up transformer.

Maybe.  The first thing I'd do is look at the transformer that's in there now 
and see if there are any additional taps on the primary winding.

> Do most transformers have taps for 110 and 220 volts?

There are a number of them out there that have the primary winding in two 
segments,  you'd connect them in parallel for 110 and in series for 220.

> There seem to be at least one unused tap on this transformer.

Measure the resistance from that "unused" tap to all of the other wires,  and 
let us know what you find.

> Also, can anyone test me how to test this transformer to find out if its
> set up for us or european voltage?

See what you find out with a resistance check.

> Lastly,  since nobody in my neck of the woods has a .2V fuse would using a
> .25v fuse cause much of a problem?

You mean .2A?  If you change the wiring of the transformer you'll probably 
need a different size fuse in there anyway,  let's get that out of the way 
first.

> I realize using a higher rated fuse defeats the purpose of using a fuse but
> should this small difference cause much of a problem?

I wouldn't think so.