My Zenith MJ-1035 radio was working very well, until I tried to push the volume control knob further onto the shaft than it was (I thought I could set the knob flush with the front panel). I turned the radio back on and heard very weak audio at first, then I lost the sound completely. Looking under the chassis, I found what could well be the problem: a broken connection on one terminal of the concentric volume pot (the inner shaft for the right channel; the other control hasn't worked since I got the radio--in fact, it looks as if it is broken
). I'm wondering where that connection goes. My Sams schematic (set 715, folder 9) is not much help, as it does not show the concentric dual pot my radio has; rather, two separate controls are shown, one for each stereo channel.
Note: I was able to get the volume control working again by temporarily connecting the broken lead to ground, so that may well be where that side of the resistance element connects.
Another problem: Several tubes in my MJ1035 are not lighting. I am at a loss to figure out why, as the MJ-1035 has a filament transformer that supposedly supplies all 11 tubes in the radio. However, I did notice from the schematic that there are two separate series filament strings, wired in parallel. I've never seen anything like this, and I'm stumped. I'm half thinking one of the tubes has an open filament, but I don't have a tube tester so I really cannot tell the condition of the filaments at this point.
This is not the first time my MJ1035 has exhibited this problem (several tubes in the filament string not lighting). The first time this happened, I was able to correct the problem by removing and reseating one tube in its socket, but that dodge didn't work this time around. I'd try replacing the tubes, but the MJ1035 uses several tubes which I've never run across, such as a 19GQ7, 19EA8 and so forth. I don't have spares for these tubes, although I can replace some of the others with tubes swiped from my other vintage radios if need be.
Thanks in advance.