Transformers,

[mrslunk]

I have an unmaked blue transformer, about as wide, deep and high as my thumb. Three pins on one side, two pins on the other.
How do i find out:
a) what it's general specs are
b) what sort of quality it is
c) where can i use it.

I'd be stoked if it were usable as a 'knockaround' DI transformer.
Any advice?

Cheers, pete

[sean k]

Those are often mini output transformers used with small power transistors. The best place to find them is in transistor radios of the sixties and early seventies. You can still buy them and they are often either 1k/8 ohms or 500/ 8 ohms but that doesn't mean thats what you have it's just quite likely the three is the outer and CT for the high impedance and the two for the speaker.

Just put 12 VAC into the primary and measure the output and do the calculations. as for power anywhere from .35 to .5W is about right.

I just used one recently from a planar ribbon capsule and it did the job quite well even if the impedances were way out from specified. I went into the 8 ohm at 200 ohms and so it'd be somewhere up around 100k out... I don't know or care because it worked!

[PRR]

The little transformers often had 2-digit model numbers, which lead you to specs.

Performance was transistor-radio quality, often 200Hz bass-cut in crude circuits, to 50Hz with special circuits and at very low levels.

In general: measure the DC resistance and multiply by 10. This will be a very approximate audio impedance. A speaker winding reads something under 1 ohm, a 1K "power output" winding will read 50-100 ohms on the meter.