11-18-2013, 02:13 PM
Radioroslyn;
OK, thanks for that input. Yes the 3.2 ohm impedance was quite popular in many radios of the late 1940s and the 1950s. I will check the output transformer as you suggested. I just finished taking a lot of pictures of cabinet and chassis. On the 40-201 the output transformer is mounted under the chassis instead of on the speaker, so at least the transformer is still there even though the speaker is long gone. I will have to decide whether to find an OEM speaker & field coil assembly or to substitute a DC choke in the power supply and use a PM speaker. I have several 12" PM speakers on hand that are 8 ohm speakers. There is much to do before I ever get to the point of chassis work. The cabinet will probably consume much of my time until colder weather hits and drives me back into the house instead of the barn.
An ultimate solution might be to use a new output transformer small enough to mount in the existing position designed to operate a 4 ohm or 8 ohm PM speaker. A transformer designed for a push-pull 6V6GT output stage would also work for the push-pull 42 tubes.
Joe
OK, thanks for that input. Yes the 3.2 ohm impedance was quite popular in many radios of the late 1940s and the 1950s. I will check the output transformer as you suggested. I just finished taking a lot of pictures of cabinet and chassis. On the 40-201 the output transformer is mounted under the chassis instead of on the speaker, so at least the transformer is still there even though the speaker is long gone. I will have to decide whether to find an OEM speaker & field coil assembly or to substitute a DC choke in the power supply and use a PM speaker. I have several 12" PM speakers on hand that are 8 ohm speakers. There is much to do before I ever get to the point of chassis work. The cabinet will probably consume much of my time until colder weather hits and drives me back into the house instead of the barn.
An ultimate solution might be to use a new output transformer small enough to mount in the existing position designed to operate a 4 ohm or 8 ohm PM speaker. A transformer designed for a push-pull 6V6GT output stage would also work for the push-pull 42 tubes.
Joe
