12-15-2021, 01:19 PM
I finished the restoration on this model 14 console. After the complete recap. I rebuilt all the Bakelite blocks and changed the filters. I brought it up on the variac and noticed that volume was low due to low gain. I touched the grid of the 6A7 mixer and it came to life. Sure enough, the antenna coil primary was open. I removed it and there it was the dreaded cotton covered wire that had green spots in it and was rotten. I used a dental tool to count the tuns before I removed the winding. It came apart in pieces. I rewound it using #34 enameled wire, it was only 6 turns. I reinstalled the antenna coil and slowly put power to the set. No change. Next I did a voltage check and found no plate voltage on the 78 RF amp. tube. Now the RF coil primary was open. I removed it and it was same thing, more cotton covered wire. This coil was 18 turns. After rewinding it and reinstalling the coil I put power to the radio, and it played well for a few seconds, then nothing. Dead radio. I suspected the oscillator coil, and I was right. The winding coupled to the 6A7 second grid was open. It was 18 turns as well. After rewinding and reinstalling the coil, the radio plays great. After doing a full alignment, its ready to go. In retrospect it was quite a bit of work and diagnostics, but in the long run I'm glad that all three coils failed on the bench rather than later on after the chassis was installed.
Mike McCrow
Mike McCrow