3.5MHz xtal Pierce oscillator using ECC83 tube at low anode volts?


OK, i'll say straight off that I have little working knowledge of tube circuits!

IM wanting to try out a simple crystal controlled Pierce oscillator circuit, using half of an ECC83 (12AX7) tube. But heres the catch - Im wanting to try this at a low anode HT!

Im looking at between 30-50v for the HT. Ive seen some ballpark figures for grid leak values (47k - 100k) and for the xtal series cap (20-120pF), but without understanding fully the specs of tubes, Im rather stumped working out the anode load resistor value, and the cathode resistor and capacitor values.

Can anyone help me out with some ballpark values to start out at?

Im using a glass encased old TV color burst crystal, an ECC83 tube and we'll say 40v HT, just to fix some of the variables. All I want to do at the moment is make the circuit oscillate. (we'll get onto using the other half of the tube as keyer/amp another time!)

I would also appreciate any simple explanations of how to go about calculating these componant values, but please keep it specific to this particular tube, as its the only one I have available!


Peter Chadwick:
I'd go for 47pf from grid to earth, 47pf from anode to earth, cathode directly to earth a 47k grid leak to earth and a 22k anode load, with the crystal between anode and grid. You can put a capacitor in series with the crystal if you like: making it variable allows frequency trimming,  but if it gets too small, the circuit will stop.

Thanks Peter,

I'll give those values a try. Ive read that the ECC83 isnt as good at lower anode voltages that the '81 and '82, but its all i have to play with of this type,

Peter Chadwick:
It's got higher amplification factor, but a somewhat lower gm. You might find some improvement by paralleling the two halves.


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