Hi:?
Not a polished circuit, but I thought this might be of interest to the group. Attached is a circuit for a simple calibrator that can be integrated into a CDV-700. It was a pain to design simple circuit that was relatively stable but could operate from a nominal 3V power supply.I believe the circuit is stable enough between 2.4V ~4.0V
I can't measure a difference in the frequency as the voltage was varied. To make it simple apply power( may be an additional front panel sw, or a hidden magnetic reed sw), and the calibrated runs off of the 3V battery in the CDV700
The output of the pulser can be always connected to the gm probe lead. The 220pF cap and circuit don't load the CDV700 enough to affect gm tube pulses. Pulse rate is fixed at about 3.6Hz 216cpm. The tolerance of 2N6027's varies quite a bit. The pulse rate can be easily tweaked. Either or both the 150k resistor and/or the 1uF cap can be adjusted.
I used a TL1431 adjustable regulator as a fixed 2.5V shunt regulator. Alternatively a? zener diode could be used. I haven't tried the zeners I had on hand ( 2.4 and 2.7V zeners)
P
