I disconnected C213 and L42 from the oscillator tube, and when I lifted up L42, it looked scorchy:
There was a layer of melted varnish sticking it to the green wire below. (I scraped that off before taking the photo.) The coil is missing varnish in the area where they touched, and some of its wires look burned black. It has continuity, measuring 2.6 ohms resistance. Not having another coil to compare, I have no idea what that figure means; if it has shorted coils, I suppose it could show continuity but have the wrong inductance.
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Originally Posted by dtvmcdonald
Try sweeping the combination of L42 and the 270 pF in parallel with it.
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I tried doing this, with inconclusive results. I can see a waveform, and I can see the waveform change in the X dimension when I sweep the generator past 3.58 mc, but I don't see anything like a peak.
It's possible I had things set up wrong. What I did was to connect C213 and L42 in parallel (but disconnected from the tube). Then I connected the sig gen at one end of this pair and the scope at the other end. I slowly changed the frequency of the sig gen and watched for a peak of some kind. Again, with my crude old generator, it's not possible to s-l-o-w-l-y vary the frequency around that exact point, or even hold it precisely, except at whatever frequency it flops to when you let go of the knob.
Phil Nelson