Mystery Machine OC79 - Where to buy/ Alternative?

[Idlebeach]

Hello pedal pals! I ordered a Mystery Machine PCB without looking at the parts list first and now I see I need a couple of germanium transistors. I have never had any luck finding germanium transistors for a decent price so I have avoided building anything that requires them.

Is there a decent place I can find some of these OC79? Is there a good alternative to them? Or if someone on here has 2-4 they could sell me that would be amazing!

I'm also curious when PedalPCB is out of stock on the mini rotary switches - where do you guys pick those up? For this build I will probably just use a toggle but I would've liked to use the rotary.

Thanks everyone!

 

[Robert]

The mini rotary switches will be available in a day or two.

 

[giovanni]

I am also looking for OC79. I do have a bag of NOS PNP Germanium transistors that I was planning to use (also as replacement for OC71). What are the hFE/leakage requirements for the Mystery Machine? High hFE, low leakage?

 

[fig]

AC128s?

Edit: Ahh...good question sir! The OC79 is in the lower gain range (from what I read) but maybe someone can fill in the blan k.

 

[giovanni]

Yeah it looks like they are slightly lower gain than OC71, but the gain ranges are so disparate…

 

[giovanni]

Not sure this page is reliable, but if so, OC79 have at hFE>=50. I tested some germanium PNPs I have and they are all between 50 and 60 (a couple >70, saving those for something else). Their leakage is consistently <40uA, which I hope is low enough.

 

[SlowAudio]

I’m getting there parts together to build the Mystery Machine. Was a bit of an impulse buy and didn’t realize there were super rare transistors involved! I’m wondering why we need to use OC79’s when gut shots of the MM show AC125’s?

 

[Robert]

I’m wondering why we need to use OC79’s when guts shots of the MMM show AC125’s?

Because the one I had used OC79's.

They're used as clipping diodes so you could surely use a substitute.

 

[SlowAudio]

Perfect thanks!

 

[giovanni]

Because the one I had used OC79's.

They're used as clipping diodes so you could surely use a substitute.

Or just plain Ge diodes. Or possibly some Si with comparable forward voltage, although you would miss out on the mojo.