> I'm trying to figure this out, I've seen a few products now where they
> place two fuse holders on the board, by putting the fuse into the
> appropriate one you set the mains voltage 230 or 115 volts.  However I
> can't figure this out, by transformer have two windings on the primary,
> with 240V you have to connect them in series and for 120 in parallel,
> how can this configuration be made using two fuse holders, one empty
> the other setting the primary configuration!?

I've never seen this done, but either of the following would work.
I'd guess they used the 2nd scheme and "wasted" a winding on 110V.

_______________________________

You can do it with 2/1 IF you allow a fuse to bridge between the ends of two 
other holders.

View diagrams in fixed width font.

          A
|---WWW---o----fff---|
|         .          |
|         .          |
|---fff---o ---WWW---|
          B

WWW = winding
fff = fuse

Insert both fuses and you have 110v operation
INSTEAD insert a fuse from A to B and you have 230 V operation.

IF the fuse holders are arranged so A is the end of one holder and B is in 
line then a fuse can be inserted between the two holders A-B.


I'd be unhappy with building anything like this !!!
Too much chance of disaster.

_______________________

If you don't mind leaving one winding unused on 110V then it's easy.

|---WWW---o- fff--o-----| 110
|         |             |
|         o-WWW--0-fff-_| 230


Insert top fuse for 110v
Insert bottom fuse for 230V

This is most likely what you saw.


        RM 
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