[ARC5] Transformers

[Robert Eleazer]

Eric:

Here is what I do with an unknown transformer:

1.  Take a VOM and sort out the pairs of wires in order to ID the windings, noting how much resistance is on each one.
2.  Take a low voltage AC source, like a wall wart at 6VAC or less or something like that, and apply that to the highest resistance winding.  Then measure the voltages on the other windings and note what the ratios are. 
3.  From that data you can figure out what is the primary and what the voltages are without electrocuting yourself or burning your house down.  
4.  Write a summary of this info down on a piece of masking tape and stick it on the top of the transformer.  This should be as close to illegible as you can make it, per tradition.

As for current capability - guess, based on size.

This is not foolproof.  I blew up an audio transformer not too long ago, working under the assumption it was for filaments.

Good luck!

Wayne