Hotcake Transistor Substitution

[GGBB]

I'm building a Crowther Hotcake clone and am wondering about the PNP 2N3906 BJT. I don't have any, but I've got 2N4126, 2N5087, and MPS3703. I'd think either MPS3703 or 2N4126 is the closer match, but are they close enough and which is closer? Since it's being used in an unconventional manner, I just don't know which specs matter most.

https://www.onsemi.com/pdf/datasheet/2n3906-d.pdf
https://media.digikey.com/pdf/Data%20Sheets/Fairchild%20PDFs/MPS3703.pdf
https://my.centralsemi.com/datasheets/2N4123-4126.PDF
https://www.onsemi.com/pdf/datasheet/2n5087-d.pdf



Rob's explanation of how it works: https://www.diystompboxes.com/smfforum/index.php?topic=125157.msg1190221#msg1190221

[antonis]

Hard to say, Gord..

Taking in mind 2N3906 is a general purpose BJT, I'd say than all of the above alternatives should be OK..
(vote for 2N5087 just because.. )

[Rob Strand]

Going back to the old National Semiconductors data, 2N3906 and 2N4126 were made using the same process.

Later on the 1997 Fairchild 2N4126 datasheet states,

"This device is designed for general purpose amplifier and switching
applications at collector currents to 10 μA as a switch and to 100
mA as an amplifier. Sourced from Process 66. See 2N3906 for
characteristics."

I don't think it's going to make a big difference anyway.