01-29-2015, 06:48 PM
I have figured out why the oscillator in this set was misbehaving. In short, it was humidity.
I had had the radio on the bench in my basement workshop for over a week since changing the oscillator cathode resistor. In that span of time, we had had several days of heavy rains. I don't run my dehumidifier in the winter, and I think that the humidity level in the basement rose enough to cause moisture to be absorbed by the oscillator coil form.
A day or two after initiating this post, where I indicated the radio wasn't working below about 950, I went back down and retested. This time, the radio wouldn't work below about 1200. Nothing at all had been done to the radio in those two days and yet it was working rather significantly worse. That was when I remembered that this coil is susceptible to moisture absorption, which impedes oscillator function.
I did find an easy way to 'dry out' the coil though. We have forced air heating, so I decided to just lay the radio on top of one of the heater vents upstairs. Two days later, I retested, and the radio works all the way to the bottom of the band.
I know that, long term, I need to rewind that coil, but I just didn't feel up to it now. And I didn't even have to remove the coil and bake it. I will have to see if this method of drying the coil works for any extended period.
I had had the radio on the bench in my basement workshop for over a week since changing the oscillator cathode resistor. In that span of time, we had had several days of heavy rains. I don't run my dehumidifier in the winter, and I think that the humidity level in the basement rose enough to cause moisture to be absorbed by the oscillator coil form.
A day or two after initiating this post, where I indicated the radio wasn't working below about 950, I went back down and retested. This time, the radio wouldn't work below about 1200. Nothing at all had been done to the radio in those two days and yet it was working rather significantly worse. That was when I remembered that this coil is susceptible to moisture absorption, which impedes oscillator function.
I did find an easy way to 'dry out' the coil though. We have forced air heating, so I decided to just lay the radio on top of one of the heater vents upstairs. Two days later, I retested, and the radio works all the way to the bottom of the band.
I know that, long term, I need to rewind that coil, but I just didn't feel up to it now. And I didn't even have to remove the coil and bake it. I will have to see if this method of drying the coil works for any extended period.
