Simulating Unijunction transistors

 I did a little on trying to simulate unijunction transistors like the 2n2160 used in the Super Whoopee circuit (shown here):

See the original post for links to the complete article:

https://wb9kzy.blogspot.com/2023/04/the-high-school-club.html

But no luck getting any output in LTspice, it must be the initial conditions, probably some kind of noise or transient is needed to kickstart the simulation.  I'll try it again some other time.

Back to the Super Whoopee, it took a while but I found my unijunction transistors, the 2n2160 (2), a HEP310 and a 2n2646.  I then tried them in the leftmost part of the Super Whoopee circuit and got these outputs:

2n2160 with 4.7 uF, 150k ohms, 9V supply

HEP310 with 4.7 uF, 150k ohms, 9V supply

2n2646 with 4.7 uF, 150k ohms, 9 V supply

Basically all are sawtooth waves although they differ in period and amplitude.  Looking at the Super Whoopee circuit there are two of these sawtooth oscillators, on the left is a slow one with a period of something like a half second.  The right oscillator with smaller values of caps and resistors must oscillate in the audio range.  The two sawtooths are mixed somehow via the PNP transistor and the 2nd unijunction.  The signal is then amplified by the 3 transistors on the right to drive a speaker.

BTW, the HEP310 was one of the HEP line of parts from Motorola, they used to be sold at AES which is probably where I got mine.  Motorola Semi is gone, AES is gone but you can still get the HEP310 on ebay:

That $1.49 net price inflates to $11 today:

I will take a look at the whole circuit on the breadboard later - maybe simulation isn't worth pursuing, the idea here is to find out how it sounds and then try to duplicate it with an easier to kit circuit.

Best Regards,
Chuck, WB9KZY
http://wb9kzy.com/ham.htm