[Radio Wrangler]

I do not know the circuit of that set, but if it has feedback from the loudspeaker output back into an earlier stage of the amplifier, it will be important to have the phase shift through the transformer correct.

If the transformer phase is the opposite of the original, instead of negative feedback, you will have positive feedback.

If this is the problem, it should be cured by interchanging which terminals the two anodes are connected to.

David