[geofy]

The AC128 connections are as the picture viewed from underneath.

A temporary way to find out if it is the transformer would be to disconnect the two emitters from a, b, windings and use just one of the AC128’s as it will need an NPN such as an AC176 as well as the AC128 to make a push-pull output. It does work as I have modified a radio with a duff transformer and it still gave acceptable volume.

Fit two resistors (quarter Watt will do, low value 2.2 Ohm minimum as shown or even up to 5 Ohm each (this is to limit the current through the transistors)

Disconnect the speaker from the transformer secondary winding , but leave the feedback resistors in circuit

Connect the emitter resistor common junction to the negative end of an electrolytic capacitor (value not critical 100uf to 1000uF 12Volt) The capacitor is to block the DC.

Connect the positive end to the speaker,

This will produce a mismatched output (that is why the output-matching transformer is there) but if there is a signal, it will show up.

It is shown with the negative at the top of the diagram

The approximate circuit is in the diagram.

Geof