Lidmotor's Penny circuit help needed.

[TinselKoala]

I just tried 2n2222 and it behaves the same, but with slightly less voltages.
Still using the same battery, and with the 2n2222 in there with collector and base swapped, the battery voltage is 382 mV.
With the 2n2222 the correct way round, the battery voltage is back to 358 mV.

And changing back to the MPSA18, battery voltage drops to 333 mV again. So the 2n2222 isn't letting as much current through it, and the battery isn't sagging as much when the 2n2222 is used. Collector peaks smaller too.

[Legalizeshemp420]

MPSA18

[Legalizeshemp420]

MPSA18 without the cap.  Notice Channel B and its settings.

[TinselKoala]

That's strange. I am using the same circuit, except without the 1.2 nF cap, and my MPSA18 keeps the 4 series LEDs lit down to a supply voltage of 0.650 volts, about, and at 1.4 volts (from DC regulated supply) the LEDs are brilliant.

[TinselKoala]

You just made me check again. I wanted to make sure I had the MPSA18 in there! And it is.
I warmed the battery using the soldering iron to raise the voltage, and the LEDs come on visibly at a battery voltage of 0.610 volts.