05-22-2009, 10:14 PM
I've been working on the radio in my basement so I brought it upstairs to see if reception was a problem. No change so it's back downstairs.
I've got a lot of noise that I can control the loudness with the volume control. There's also a good deal of buzz noise that's the same regardless of the tuning frequency. On talk radios stations, the voices are garbled. The louder they speak, the more garbled it sounds, just like turning up the volume. Guess it time to start reading about motorboating again.
I looking at the schematic and there's a 3.5 ohm RF coil in series with a 100 pf mica capacitor between the RF tube plate and the Det-Osc tube grid. The ohms are hard to check because it's in parallel with a 10k resistor (guess that shouldn't affect it that much). The wax coating is cracked and I can see the copper wires through the cracks. The mica capacitor looks dirty and both are very close to an solder lug so I don't want to get into that much with a hot iron. If I were to replace the capacitor I would simply clip it off and clean a point as far as possible from the coil to reconnect. I may even scrap enough old wax from all of those old paper caps to seal the coil.
What substitutes for mica capacitors now? Good grief, what substitutes for a 3.5 ohm rf coil (an inch long and about 1/4 diameter). There's 180V going into the coil so it looks I put my solid-state capacitor stock away for another project.
I've got a lot of noise that I can control the loudness with the volume control. There's also a good deal of buzz noise that's the same regardless of the tuning frequency. On talk radios stations, the voices are garbled. The louder they speak, the more garbled it sounds, just like turning up the volume. Guess it time to start reading about motorboating again.
I looking at the schematic and there's a 3.5 ohm RF coil in series with a 100 pf mica capacitor between the RF tube plate and the Det-Osc tube grid. The ohms are hard to check because it's in parallel with a 10k resistor (guess that shouldn't affect it that much). The wax coating is cracked and I can see the copper wires through the cracks. The mica capacitor looks dirty and both are very close to an solder lug so I don't want to get into that much with a hot iron. If I were to replace the capacitor I would simply clip it off and clean a point as far as possible from the coil to reconnect. I may even scrap enough old wax from all of those old paper caps to seal the coil.
What substitutes for mica capacitors now? Good grief, what substitutes for a 3.5 ohm rf coil (an inch long and about 1/4 diameter). There's 180V going into the coil so it looks I put my solid-state capacitor stock away for another project.
