09-22-2025, 08:33 PM
I thought about hooking up the scope; one trace from the bucking winding, the other from the field coil to see if they are out of phase.
And yes the coil polarity would change the N and S of the pole, “right hand rule” and all that. I would not think it much matters if the cone moves outward or inward on a positive pulse though. Even though the coil is random wound, all the turns are in the same direction. I believe that reversing the field coil wires would also change the phase of the ac component induced in the pole.
I have about 2.6v of 120hz at the output of the field, and about 4mv at the bucking coil, which seems to totally eliminate any hum from the speaker with the volume control at minimum.
Radio is a Philco 38-7XX with a H31 speaker.
And yes the coil polarity would change the N and S of the pole, “right hand rule” and all that. I would not think it much matters if the cone moves outward or inward on a positive pulse though. Even though the coil is random wound, all the turns are in the same direction. I believe that reversing the field coil wires would also change the phase of the ac component induced in the pole.
I have about 2.6v of 120hz at the output of the field, and about 4mv at the bucking coil, which seems to totally eliminate any hum from the speaker with the volume control at minimum.
Radio is a Philco 38-7XX with a H31 speaker.
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