How to assurtain OT OHMs ??

I have two amps, one I have schematic for, the other nothing on the web. Schematic does no specify, and the other I got nothing other than a working amp. they both work FWIW.

1st, Webcor 1960 2 EL84 tube amp, 2nd a 70s Bruce Bass Amp/Cab with the 100 watt SS amp in the 410 amp/cab, and made to have the pre-amp sit a-top.

Short of reading the volts on the primary VS secondary hot and doing math, is there a way to ascertain correct OT load when not marked and not hot?

Thanks

Bump. I wanna know a down and dirty way, too.

I gotta story about unwinding one at work during lunch in the parking lot when we were just curious and really board. It was a slow day.

If one were to simply want to replace an output transformer that was defective, you just need a tube manual to tell you the needed load. You need to know the plate voltage, grid bias, dissipation and desired output load, etc.

To measure an unknown transformer, you need something like an LCR bridge that measures the transformer primary reactance. This is done with a A.C. signal, 1KHz signal for audio components.

I use a Fluke LCR bridge in the Metrology lab at work. It's fascinating & revealing to measure transformers, capacitors and resistors with an AC signal! But, I digress...