03-16-2015, 10:07 PM
It's taken me a long time to finish this, but I finally replaced the converter tube socket and baked the oscillator coil in the oven for an hour with the oven set at 200 degrees F. The thermometer inside the oven tells me it only got to about 160, but I don't know if that's accurate or not.
Once I had the coil out and baked, but before I put it back in the radio, I measured the DC resistance between pins. I should have done that before baking, but it didn't occur to me. Between pins 2 and 3 I got 68 ohms, where the schematic tells me I should have 1.5 ohm. I scratched my head over that for a few minutes and then decided to reflow the solder on the pins to see what happens. After several tries I got the resistance down to about 6 ohms. It wouldn't go any lower. The resistance between the rest of the pins is about nominal, maybe just a little high, so I left them alone.
I put the coil back in, and now I get signals across all three bands. The SW signals are weak, but I just have the loop antenna propped up behind the chassis on my basement workbench, which is not the best place to listen to short wave. Still, now I know the oscillator is working on SW, which it wasn't before.
I'm not sure whether it works because I baked the coil or because I reflowed the solder, but at any rate it's working. Next I'll do a complete alignment and see how things sound after that. I haven't touched the SW alignment since I recapped the radio in 2007, so maybe aligning it will improve things.
Once I had the coil out and baked, but before I put it back in the radio, I measured the DC resistance between pins. I should have done that before baking, but it didn't occur to me. Between pins 2 and 3 I got 68 ohms, where the schematic tells me I should have 1.5 ohm. I scratched my head over that for a few minutes and then decided to reflow the solder on the pins to see what happens. After several tries I got the resistance down to about 6 ohms. It wouldn't go any lower. The resistance between the rest of the pins is about nominal, maybe just a little high, so I left them alone.
I put the coil back in, and now I get signals across all three bands. The SW signals are weak, but I just have the loop antenna propped up behind the chassis on my basement workbench, which is not the best place to listen to short wave. Still, now I know the oscillator is working on SW, which it wasn't before.
I'm not sure whether it works because I baked the coil or because I reflowed the solder, but at any rate it's working. Next I'll do a complete alignment and see how things sound after that. I haven't touched the SW alignment since I recapped the radio in 2007, so maybe aligning it will improve things.
John Honeycutt
