R1 is 2.2k Ohm with a 12 VAC transformer. Here are some sample traces.
A 2N383 Emitter to Collector. It is a negistor see the reverse break over?
This one is a capacitor. Ideally it would be an oval but my digital scope doesn't seem to understand oval
This one is an Emitter to Base curve.
A 2N2222 Emitter to Collector.
A GS109 Emitter to Collector.
Another Emitter to Collector.
Power diode no breakover at top.
A resistor.