10-02-2017, 12:56 PM
I have been restoring a Crosley 106CP for a friend. This is a 10 tube chassis with AM/SW and phono input from a console. I think it is either immediately pre-war or immediately post-war, as it was full of the crumbling rubber-coated wire.
It works perfectly in my basement workshop, but installed in the cabinet at the owner's house, there is a fairly strong modulation hum. It hums whenever I tune into a station. In between stations, no hum.
I've tried all the common solutions for modulation hum listed in Marcus and Levy. 1) Line filter cap, 2) RF Tube, 3) Converter Tube. I've made sure the antenna is connected properly. Nothing made a bit of difference.
I figured I missed something, so I brought it back home to check out again. I dummied up a loop antenna of the same dimensions and orientation as in the cabinet, and the radio performs strongly with no hum. But it hums in the cabinet at the owner's house all the same.
If anyone has a possible solution or something else to check, I would appreciate it.
It works perfectly in my basement workshop, but installed in the cabinet at the owner's house, there is a fairly strong modulation hum. It hums whenever I tune into a station. In between stations, no hum.
I've tried all the common solutions for modulation hum listed in Marcus and Levy. 1) Line filter cap, 2) RF Tube, 3) Converter Tube. I've made sure the antenna is connected properly. Nothing made a bit of difference.
I figured I missed something, so I brought it back home to check out again. I dummied up a loop antenna of the same dimensions and orientation as in the cabinet, and the radio performs strongly with no hum. But it hums in the cabinet at the owner's house all the same.
If anyone has a possible solution or something else to check, I would appreciate it.
John Honeycutt
