The PHILCO Phorum

I just finished rewiring and recapping my 42-355. I get nothing but some hum, so I'm starting the troubleshooting process by measuring voltages. The B+ seems to be low, compared to the schematic values.

The AC is about 121 volts, and the output of the rectifier (across the 1st filter cap) is 277 VDC instead of the 290 on the schematic. The B+ across the second filter is about 165 instead of 190, and I get 160 and 165 at the plate of the two 41 output tubes. Schematic values are 185 and 190. I didn't replace the candohm resistor because the resistances are close to spec, but I could try that next.

I'm not sure this is enough difference to matter, but I thought I'd ask some wiser heads here on the forum before I went any further. I'm concerned that the plate voltage on the oscillator XXL will not be enough if the B+ is 25 volts low.

I get audible clicking when I touch my soldering iron onto the plates of all the tubes except the oscillator, but I don't get anything when I inject a 455KHz modulated signal into the signal grids of any of the tubes, so I might have wired something wrong somewhere.

Any thoughts? I have another 42-355 chassis that I could pull the power transformer from if needed to get the proper B+ voltage (assuming that transformer is good.)

Update. I looked around for wiring errors, and found that I had forgotten to reinstall the triode plate load resistor for the XXFM (part 79). I put that part in and remeasured the plate voltages again. All were 10-25 volts low, except the oscillator tube, which was about 50 volts high. There was no voltage drop across the plate load resistor for the oscillator, so I figured the oscillator wasn't working. I replaced the oscillator XXL, and the radio started to work, but the plate voltage on the oscillator was still way too high. I played around with different oscillator tubes, and discovered the tubes were not making good contact to the socket. I cleaned the socket and solved that problem. No change in the oscillator plate voltage, though.

I replaced the candohm resistor strip with modern discrete resistors. When I removed the original, it measured out OK, but for some reason the oscillator plate voltage is now a little bit low, the same as all the other tubes.

I get good reception on all bands. I even get strong reception on FM, picking up stations from the bottom half of the modern FM band at about 1/2 of their actual frequency. I don't know how this happens, but it seems to work.

I aligned the AM and SW bands, and now I get good strong reception everywhere. I decided not to touch the FM alignment, since the instructions are confusing, and since I mysteriously get good reception on that band. However, when I set up the AM push button coils and compensators, some of the stations on the push buttons came out MUCH stronger than when I tuned those same stations on the dial, others not. I'm really not sure why this should happen. Maybe the antenna compensator for the broadcast band? When I turn that compensator, not much happens.