More curve tracing fun. Apologies for the slight parallax...I grabbed this with my phone as I felt too lazy to set up my tripod and dSLR. I really need to move forward with modding the C-12 camera I have to admit a modern camera.
Anyway, I could have really used this when I was building Jim Williams pulsers. Rather than guess at when your transistor might avalanche, you can determine exactly where it will avalanche. The setup is a pair of otherwise identical NOS Motorola 2N2369, the same transistor Jim used. Note that the first one is not avalanching at all at 30V on the collector sweep, but the second one is. The first requires significantly more voltage before it will avalanche. Settings are 30V collector sweep, .5 mA/div vertical, 5 V/div horizontal, .02 mA/step, and 5K dissipation limiting resistor selected.