[morzh]

What is more important, however, is that this transformer needs to have a primary impedance of 12,400 ohms to match a 1.25 ohm impedance voice coil.

You can't measure impedance with your ohmmeter...but you'll need this info if/when you replace that audio output transformer. A Hammond 125D will work as a replacement; connect the voice coil to output terminals 4 and 5. It won't match exactly but will be very close.

Marv,

This (what Ron just said) means that your output to input windings turn ratio should be 100 (the input impedance is the output impedance time square of the turn ratio).

So when you have your Hammond replacement XFMR, look at the table and choose the taps that give you primary to secondary turn number ration equal 100.

Although as I remember, the table actually lists the input impedance vs. Voice coil resistance.