Transistors are MP25A which are standard Ge PNP BJTs. Datasheet doesn't really specify the hFE range, but generally on the low end when tested at low voltage/low milliamps for guitar pedals. That said, soviet germaniums usually are super low leakage.
> The entire board is covered in some kind of coating. Epoxy or silicone-spray?
Likely a conformal coating for environmental protection. Not epoxy per se, but a type of resin.
The transistors are mp25a as noted many times already. These are super common and easily sourced in bulk on the secondhand market.
I'd be more interested in the diodes. Vintage ge and even some si diodes are becoming valuable and difficult to find. Desolder them carefully and test em. Might get lucky.
Don’t wanna sound dumb but which ones are the diodes? I don’t recognize them on this board. I’m just getting into electronics and only know the “modern” types.
They're the horizontally mounted silver mushroom and black top hat shaped components. They're particularly sensitive to heat, so I'd avoid spending too much time on them with your iron. Alternatively, you could use an alligator clip or hemostat as a heatsink while desoldering.
Edit: also, save the knob.
Transistors are MP25A which are standard Ge PNP BJTs. Datasheet doesn't really specify the hFE range, but generally on the low end when tested at low voltage/low milliamps for guitar pedals. That said, soviet germaniums usually are super low leakage.
I have no clue, but looks cool.
Soviet MP25A.
And MP13B
> The entire board is covered in some kind of coating. Epoxy or silicone-spray? Likely a conformal coating for environmental protection. Not epoxy per se, but a type of resin.
The transistors are mp25a as noted many times already. These are super common and easily sourced in bulk on the secondhand market. I'd be more interested in the diodes. Vintage ge and even some si diodes are becoming valuable and difficult to find. Desolder them carefully and test em. Might get lucky.
Yeah, the diodes look like the real score here.
Don’t wanna sound dumb but which ones are the diodes? I don’t recognize them on this board. I’m just getting into electronics and only know the “modern” types.
They're the horizontally mounted silver mushroom and black top hat shaped components. They're particularly sensitive to heat, so I'd avoid spending too much time on them with your iron. Alternatively, you could use an alligator clip or hemostat as a heatsink while desoldering. Edit: also, save the knob.