An oscillator for Mr. Williams

Could be the base ringing when reverse biased. I usually add a small = resistor (maybe 22 ohms in this size) to dampen it and soften forward = base current.

With the tank, you'll be looking at something more "class C self = excited", too.

You should be able to get a coathanger to glow red inside that coil.

Tim

--=20 Deep Friar: a very philosophical monk. Website:

turns=20

output=20

(maybe 22 ohms in this size) to dampen it and soften forward base current.

I'll give that a try - the ringing seems to happen right when the transistor goes back into cutoff after the current pulse so that seems plausible. I think I'd better add a protection diode as the reverse bias is coming pretty close to the base-emitter junction limit.

I misunderstood the operation of the circuit somewhat, but after setting it up in LTSpice and looking carefully at the waveforms plotted together it makes sense now. The transistor is in cutoff most of the time, and only comes up out of cutoff briefly, when the collector has swung all the way down, to deliver a current pulse into the tank. It then goes back into cutoff again as the tank swings back up.

Nice! I'll give it a try and report back.

Be careful when you do that -- the base ordinarily consumes current, = which is good because it sets bias. With a reverse diode, bias goes = both ways, and the transistor stays about half on... phut, bang.

One thing you can do is add a series diode, so it only turns on. But = with nothing to remove charge, the transistor stays on. So you can add = a capacitor to bypass the diode and suck some charge out. Or you can = add a current-limiting transistor, so it stays on until the current = reaches the limit, then shuts off. This would put operation closer to = class E, where you get a big flat spot while the transistor charges the = inductor.

Tim

--=20 Deep Friar: a very philosophical monk. Website: