[Amps] LF oscillation caused by defective plate choke?

[peter chadwick]

Paul,

1000pF is 45 ohms at 3.5 MHz. If the plate choke is 250 microhenry - typical value - that's 5500 ohms. There's around 2kV RMS of RF on the plate, so that's 360mA of RF in the choke and 16 volts of RF across the 1000pF. I think that one is better off with a larger bypass - 3000pF say - and then another RF Choke (which can be a lot smaller) and another bypass capacitor to keep RF out of the power supply - some electrolytics don't like much RF current.

It gets even worse on 160, though.


73

Peter G3RZP