NKT275 transistors circuit protection

[VSmolsky]

Good evening everyone,
I would like to know if by powering 3 NKT275 germanium transistors with the wrong polarity (center-negative), they can burn out and make the pedal no longer work.
I refer in particular to the Fulltone Soul Bender V1 bigbox, I found one not working. I would like to understand if one of the possible causes could be that the owner accidentally powered it with the center-negative polarity, frying the 3 NKT275 transistors.

AFIK, if there is a protection circuit, it is possible to use the wrong polarity as well without damaging the pedal. I googled the schematic to find it out, but I only found this. I don't know if it's accurate or not.



Can you help me? I would like to know if I'm going to buy a pedal that can be easily repaired (a new switch, a new potentiometer) or that need a new set of NKT275s (ouch!).
Thanks a lot

[idy]

Yes, quite sure this exact problem came up here last year(?) or so. FullTone. Some one plugged into a "normal" (for pedals) center neg even though the box was labeled something like "tip positive" and fried the transistors.


Have not found the thread. Pretty sure the issue was they didn't even add a protection diode. Save a penny, fry a pedal. Voids warranty... no problem.

[VSmolsky]

Yes, quite sure this exact problem came up here last year(?) or so. FullTone. Some one plugged into a "normal" (for pedals) center neg even though the box was labeled something like "tip positive" and fried the transistors.


Have not found the thread. Pretty sure the issue was they didn't even add a protection diode. Save a penny, fry a pedal. Voids warranty... no problem.

Could you please help me find the thread? I found this one about a non working Soul Bender, but it's very old (2010)
https://www.diystompboxes.com/smfforum/index.php?topic=83351.0

Because we're still talking about €180, not exactly a very low figure. If there is no protection circuit on the transistors, then that is very likely the problem, because a pedal doesn't stop working overnight.

[duck_arse]

https://www.diystompboxes.com/smfforum/index.php?topic=129152.0

"A pricey used pedal arrived non-functioning - is it a simple fix or a return?"

search "fulltone polarity", easy peasy.

[VSmolsky]

https://www.diystompboxes.com/smfforum/index.php?topic=129152.0

"A pricey used pedal arrived non-functioning - is it a simple fix or a return?"

search "fulltone polarity", easy peasy.

Thanks for the link.
From that thread I can say that the pedal doesn't have a protection circuit, and powering it the wrong polarity tip (center-negative) won't fry the transistors. Or maybe the OP was lucky because he powered it for a short time with the center negative tip, I don't know...