Some radios used speakers with three wire fields. If open we usually mention to replace the speaker or rewind the field. You don't necessarily need to do this.

Is one section of the field is open just bypass it with a resistor. The good section is often enough to power a speaker magnet. You may not notice any difference in sound quality, I don't.

Norm: What was the reason for the three wire field coil? Only part of the coil used as a choke filter in the power supply? Just curious.

Regards,
Ron

Hi Ron

The entire field coil is still used as a fiilter choke. Most fields had too high of a voltage drop to bias the output stage directly. A resistor voltage divider was often used across the field to develop bias voltage. The third wire was a field tap so the resistor divider wasn't needed.

Didn't think about it before but a speaker plays well even with one part of the field open. Just bypass the open section with the proper wire wound resistor.