Transformer identification

[Grant Richter]

As I recall an article in Popular Electronics from the 70s...

A Variac is a variable output transformer that can go from 0-130 VAC.
The idea is to put a AC current meter and AC voltmeter on the output
of the Variac. You can then set the current and voltage to some reasonable
power level (like 100 milliwatts). Since most power transformers will take
a
tenth of a watt into either winding without blowing up.

You can then measure the voltage out of the other winding and get
the turns ratio. Even if you get it backwards, the power level
is limited. Bear in mind that most variable transformers are not
isolated from line hot, so treat the whole circuit like it's hot.

----------
> From: J. Larry Hendry <jlarryh at iquest.net>
> To: Synth-DIY <synth-diy at mailhost.bpa.nl>
> Subject: Re: Transformer identification
> Date: Monday, August 09, 1999 7:05 PM
> 
> > From: Tim Nowaczyk <zimage at cs.wisc.edu>
> >      I found a few old TV transformers and I was wondering if there is
an
> > easy way of determining the values without destroying them.  On has
about
> > seven or ten wires comming out of it and is very large, so simply
putting
> > a voltage across some wires and testing the secondaries is out of the
> > question.
> 
> (and quite dangerous) 
> 
> But, that brings up an intersting question.  Is there anyway to quickly
> check the ratio of such a transformer from winding to winding.  We have a
> simple-to-use tester at work (but probably not cheap) that we use to
verify
> the ratio of large power transformers (as part of a series of testing). 
> Anybody know how these work?  Knowing the ratios of a transformer and
> something about the original application could easily lead one to the
> appropriate connections and voltages.
> 
> Larry H