INFANEM the driving notion clone

[Schlatte]

is the 470k on the base of Q6 really going to VCC? Could it be that it is going to Q6 Collector? Would be more logical, although 470k is pretty low for a single bias resistor? Could be a 4M7 maybe?

[imJonWain]

Look's to go to VCC.


I'm not 100% sure on the pin connections on these two, it could be something odd?

[Schlatte]

what I find suspicious is the strange pinouts those SOT23 Devices would have to have to work as in the Schematic as "normal" NPN BJTs... I've never come across one that has the Emitter on the single middle pin, it's always one of the two pins...
additionally, Q5 and Q8 in your trace are soldered correctly on the designated footprints, where Base, Collector and Emitter pins seem to be correcly connected in the layout, just the other two needed to be rotated. An SMT 2n5088/2n5089 and 2n2222 have the same pinout, so it would've worked without having to rotate the chips.
My guess is that those are not NPN BJTs.

[Schlatte]

Do you know if the rotated SOT23s were also flipped upside down (no marking visible)? because if you would rotate and flip them, the base would be on the correct spot again - then you could use a PNP in some strange configuration... let's just assume for a moment those are PNPs, pinout would be:
...3...
...|...
.|..|.
.1..2.
1=Base
2=Emitter
3=Collector
If they are then flipped, Base and Emitter swap places. Then the Pinout with Collector on 3 would make sense again, but the circuit still doesn't, really...

[imJonWain]

I never had the pedal in person so I'm not sure if they are upside down or not. Even upside the standard sot23-3 NPN trans package doesn't match up. I thought maybe miss used PNPs or perhaps FETs?

My only guess on the footprint is they used the exact same footprint for every transistor. The pedal had a through hole J201 soldered to the same smt footprint pads for the first stage. Dunno.

Shoot me a PM if you want and I'll send along the photos to ya.

[Schlatte]

I just checked the pictures from the google drive link that was posted in this thread before, there are no markings visible on those two parts, so I'm guessing they're flipped. I checked the standard SOT23 pinouts for P and N Channel FETs and that wouldn't make sense either... I'm guessing it is some PNP type. The other transistors have SMD Code 1P6, which is 2N2222 or BC847, so that should be correct.
If we assume that those are indeed PNP transistors in some fucked up configuration, I could try to just swap out the BJTs on my build for some PNPs I have laying around and see what it does. Best would be to unsolder those two and check for the marking on the other side. That could also reveal maybe some strange connection under one of those parts? But nothing is visible from outside, my first guess was some butchered push/pull stage or something but it doesn't seem so...
I'll try to build up one version with the PNP idea but it might take a while... if anyone else has a setup where they could easily swap out the Transistors that would be perfect. Mind the Collector/Emitter Pinout if you choose to try it (Collector goes where the Emitter is drawn now)

[imJonWain]

I'm gonna toss some sockets in on my board and play around a bit.

[Schlatte]

[imJonWain]

An sot23-3 jfet (J201) right side up would fit correctly on the pads.

edit: you're right, dunno what package I was looking at.

[Schlatte]

Nah, the jfets have the gate on pin 3.

[mcatano]

If anyone needs a gut shot of an actual pedal for any reason to help diagnose, I'm happy to crack mine open. Thanks for trying to sort out the build, folks.

[goroth]

If anyone needs a gut shot of an actual pedal for any reason to help diagnose, I'm happy to crack mine open. Thanks for trying to sort out the build, folks.

Rad!

Is yours through-hole or SMD?

[mcatano]

SMD, and it loks like everything aside from the jacks are board mounted with component side down.

(5-knob, white case w/ black print)

[imJonWain]

I would love that, I'll shoot you a pm.

I just tried playing around with PNPs for the mystery parts and it does stop oscillations but as one would expect, kills the volume on that leg of the circuit. I'll keep toying around.

Another possible factor is capacitor values. Ceramic SMD caps loose effective capacitance quite a bit when DC biased.

[Schlatte]

nice! just be careful with disassembling/assembling the pedal, apparently they're not the best build quality. We wouldn't want you to break your pedal.
Who has the original Pedal from where the Trace was made, btw? Is it still at EYG? Maybe he can unsolder one of those SOT23s and check the marking or use a BJT checker to verify the PNP theory?