FrankieKat
Recapped
Caps replacement almost done. Not surprisingly, every paper cap was either a total dead short or near dead short, so all were replaced. Resistors, same -- all but one were way out of tolerance, so had to go as well.
Replaced the incorrect value tone control with a new one -- fortunately a 50k single pot is very attainable. Put in a temporary 500k (stereo) pot with a 330k resistor across it to give close to the 200k called for by the schematic. I'll probably have to do the same thing if I end up using a new volume control since I don't think it'll be so easy to find a 200k audio pot with AC switch and a 1 1/2" shaft. Yes, I know that will throw off the volume taper in rotation, but for a radio like this I don't think it'll matter much. Besides, I kind of like the smooth feel of the two brand new pots at the moment. :)
First power up, this thing sounds great. Without touching the alignment, and despite missing two tube shields and the PT center-tap-to-ground cap (d'oh!), the AM is clear as a bell and has amazing full-frequency sound and very solid bass. I hate to say it, but it sounds a bit better than the Philco. The shortwave isn't quite as sensitive as the Philco, but it seems to have better noise rejection so I'll call that a draw. Then again, maybe an alignment will pull the Zenith ahead.
Next up... clean the filthy chassis and parts. Going to add a fuse and thinking I might add a 10ohm 10W resistor in series with the AC cord to drop the line voltage down about 5V or so (the set draws exactly 0.5A on the AC line) to get the B+ closer to spec. I've found that 115VAC on the variac gives near perfect DC voltages so even if the supply voltage is slightly lower than 120VAC it'll just make the set run a little cooler rather than hotter.
Recapped
Caps replacement almost done. Not surprisingly, every paper cap was either a total dead short or near dead short, so all were replaced. Resistors, same -- all but one were way out of tolerance, so had to go as well.
Replaced the incorrect value tone control with a new one -- fortunately a 50k single pot is very attainable. Put in a temporary 500k (stereo) pot with a 330k resistor across it to give close to the 200k called for by the schematic. I'll probably have to do the same thing if I end up using a new volume control since I don't think it'll be so easy to find a 200k audio pot with AC switch and a 1 1/2" shaft. Yes, I know that will throw off the volume taper in rotation, but for a radio like this I don't think it'll matter much. Besides, I kind of like the smooth feel of the two brand new pots at the moment. :)
First power up, this thing sounds great. Without touching the alignment, and despite missing two tube shields and the PT center-tap-to-ground cap (d'oh!), the AM is clear as a bell and has amazing full-frequency sound and very solid bass. I hate to say it, but it sounds a bit better than the Philco. The shortwave isn't quite as sensitive as the Philco, but it seems to have better noise rejection so I'll call that a draw. Then again, maybe an alignment will pull the Zenith ahead.
Next up... clean the filthy chassis and parts. Going to add a fuse and thinking I might add a 10ohm 10W resistor in series with the AC cord to drop the line voltage down about 5V or so (the set draws exactly 0.5A on the AC line) to get the B+ closer to spec. I've found that 115VAC on the variac gives near perfect DC voltages so even if the supply voltage is slightly lower than 120VAC it'll just make the set run a little cooler rather than hotter.