big muff debug help?

[adapt]

hi guys, built a muff clone for my friend, sounded great, but the volume pot was faulty so I fixed it.

he took it home, then it stopped working. i suspected a loose socket (those tayda sockets are terrible). i knocked on the pedal, it roared back to life. no problem, i'll just put a little dab of solder on the sockets.

this is where the trouble started. after having a heck of a time soldering inside the sockets in a completed build, i opted to remove the sockets entirely and solder the two transistors (q3 and q4) directly to the board.

after doing this, the pedal sounds great, but just one problem: it's unity with volume ALL THE WAY UP. heck, it might even be slightly quieter. anything below this and is definitely below unity.

at first, q4 collector voltage read as 11v (my 9.6v wall wart gives that off) until i replaced the collector resistor, now it is normal. here are the voltages:

Q1
C 5.88
B 0.77
E 0.04

Q2
C 6.02
B 0.75
E 0.04

Q3
C 5.41
B 0.77
E 0.04

Q4
C 6.0
B 2.03
E 1.29

as you can see, q4 is the outlier, B,E is all messed up. i removed it from the board and tested with the DCA and it gave me normal readings, i.e. it doesn't say anything about it being bad.

it was subject to a lot of heat during the socket removal, did i just torch it or what?

any help is appreciated.

[adapt]

according to some looking around, q4 appears to be ok-ish. i also swapped q4 out for a new part and it sounds the same

what the dink is going on here

[Frank_NH]

Check Q4 again - that emitter voltage looks too high.  Maybe the transistor needs to be replaced.  Here are some typical voltages for your reference:

[Ciaran Haslett]

Also check its resistors for cold joints/wrong values.

[Frank_NH]

I don't think it a wrong part as the effect was working before.  Transistor may have fried.  Cold solder joint is a possibility too (don't ask me how I know this ).  Good to check everything!

[Ciaran Haslett]

I missed the part where it already worked sorry.  In that case yeah a bad joint is possible, or a stray burr from a cut that was missed when built but has now found its way to bridging tracks.  Thats what killed my Pink Purple fuzz for a few days after going solid for a year

[adapt]

hi guys, thanks for the help. i reflowed every joint around Q4, and as i stated before, i swapped it out for another of the same part, with the same results. the iron was turned up super hot when i was desoldering the sockets, any chance i cooked some resistors around Q4, such as the emitter resistor? it's literally the only thing i haven't tried that makes any kind of sense.

[Frank_NH]

I doubt the emitter resistor is damaged but you could check with your DVM.  You can also try jumping the resistor with another of the proper value.  Also, try replacing Q4 again - it may have been cooked.    That's all I can think of, unless there is a cold solder joint or solder bridge somewhere else.  Good luck.