04-08-2014, 03:24 PM
You will probably have a hard time finding a replacement choke, as its inductance is most likely in the 20 to 50 Henry range. It is wound with literally miles of very fine wire, which allows a very high inductance in a small physical size.
The most available replacement would be to use the primary winding of an interstage audio transformer as a substitute for the choke, leaving the secondary winding unconnected. It would have an inductance comparable to the original choke winding.
Another possibility would be to use the resistor instead of the choke and increase the value of C27 to 10 uF or more. This would compensate for the loss of filtering by the choke, and would closely approximate the type of filtering used on later more modern radios.
I doubt the volume problem is related to the open choke, now that you have bypassed it with the resistor. This radio uses a very complicated biasing scheme to provide AVC and volume control, so the loss in volume control could be caused by a problem anywhere in the bias or AVC circuits.
The most available replacement would be to use the primary winding of an interstage audio transformer as a substitute for the choke, leaving the secondary winding unconnected. It would have an inductance comparable to the original choke winding.
Another possibility would be to use the resistor instead of the choke and increase the value of C27 to 10 uF or more. This would compensate for the loss of filtering by the choke, and would closely approximate the type of filtering used on later more modern radios.
I doubt the volume problem is related to the open choke, now that you have bypassed it with the resistor. This radio uses a very complicated biasing scheme to provide AVC and volume control, so the loss in volume control could be caused by a problem anywhere in the bias or AVC circuits.
