A-man Sunface NKT 275 DEAD! Can you help?

[FirstTimer007]

I have been asked to repair an Analogman Sunface NKT275.
I was told it went intermittent, now nothing when effect engaged, it passes bypass signal fine.
Stomp switch tests fine, have traced continuity with DMM, checked voltages which seem unusual.
Hoping trannie Q1 hasn't died?
Voltages:
Battery 9.1V
Q1 C   0.08V
Q1 B   0.08V
Q1 E   0.0 V
Q2 C   8.1V
Q2 B   0.08V
Q2 E   0.04V
No sound at all with effect engaged.
Tried R.G.'s 'Audio Probe' also.
I'm at a loss now.
Cheers

[tonyharker]

Looks like it.  Is in a socket? 
A suitable replacement for a NKT275 should be an AC125.

[FirstTimer007]

Thx Tony!  The transistors are soldered in too, bummer! Not looking forward to letting the owner know, he's s fine player, and this was his favourite fuzz! I'll try to find an AC125. I have a few Toshiba SB56 PNP Germs maybe one of those would sound close?

[GGBB]

Tried R.G.'s 'Audio Probe' also.

And what did that tell you? Where does the sound stop?

Q1 might not be dead - bias is way off for certain. For reference: https://www.electrosmash.com/fuzz-face. You should be seeing around -4.5V at Q2C with -9V power. Your other voltages are in the ballpark assuming the values are actually negative. Q1B is a little off, but that may be due to Q2C being way off.

[Electric Warrior]

I have been asked to repair an Analogman Sunface NKT275.
I was told it went intermittent, now nothing when effect engaged, it passes bypass signal fine.
Stomp switch tests fine, have traced continuity with DMM, checked voltages which seem unusual.
Hoping trannie Q1 hasn't died?
Voltages:
Battery 9.1V
Q1 C   0.08V
Q1 B   0.08V
Q1 E   0.0 V
Q2 C   8.1V
Q2 B   0.08V
Q2 E   0.04V
No sound at all with effect engaged.
Tried R.G.'s 'Audio Probe' also.
I'm at a loss now.
Cheers

What's the temperature? Looks like it could be a heat related problem. It may be gating so bad right now that it's not passing signal anymore.

[willienillie]

Intermittent, then dead, suggests a flakey connection to me.  That connection could be inside a transistor sure, but IMO more likely somewhere else.

[mth5044]

Might be worth talking to AnalogMan. Seems like an odd failure, may be covered under a warranty or something.

[alexradium]

Might be worth talking to AnalogMan. Seems like an odd failure, may be covered under a warranty or something.

yeah,a stupid fuzz face at that price should be under a lifetime warranty imho.

[pinkjimiphoton]

mike's a good dude, definitely talk to him.

voltages look like the b/c is shorted on q1. could be static related, but i'd guess from personal experience the q is hosed. sometimes they will short just from leakage, especially if they've gotten hot. i killed quite a few ge's till i learned to leave the leads long and use heat sinks.

[duck_arse]

have tin whiskers ever been a thing with the NTK's?

[pinkjimiphoton]

from what i understand, yeah, could happen with any old transistors if the environment is right for it.  fascinating stuff, that. but it sure looks to me to be thermal runaway or shorted c/b

thermal runaway can def mimic a shorted, misbiased transistor

[Electric Warrior]

mike's a good dude, definitely talk to him.

voltages look like the b/c is shorted on q1.

It looks like it, but with a collector voltage that low, the base is usually within 0.01V even if the transistor is fine, so it could still be a temperature related issue.

[pinkjimiphoton]

yeah, for sure bro.
i remember one fuzzface i had that sounded PHENOMENAL between about 65 and 85 degrees. below that, i had to blast hot air into the jacks with an embossing tool  to warm it up or it was wicked farty... too hot, and i'd have to stick it in a baggie in a cooler or fridge between sets... it would be SCREAMIN then die

but honestly, i think for the price being charged, it should be waranteed for life.  you're paying more for the name than the circuit imho, and well deservedly, but... tonally? pretty much any dang ge in the proper gain range is gonna sound pretty similar unless you're a true cork sniffer. nk275's can sound great, or like total ass. i gotta red dunlop
"da" and a blue one as well. both use nk275's in them.

the red one sounds @#$%ing phenomenal always, but tends to die when the battery drops too low. the blue one CAN sound great, but only if some evil covenant somewhere is sacrificing small furry beasts to cthulu during a blood moon.
its dicey. can sound ok, but nite and day difference. it sounds more like the aqua jimi hendrix variant i gave away, the silicon model.

i highly doubt all these transistors are tested for TONE. tested for leakage and gain, yes. when i worked for some one whom i'm not gonna mention, i populated a few fuzzes for them with the procured ge transistors, and tested them with one of them high fallutin' peak testers that tests for everything, and they were transistors being used in commercial products that i would not use in my own builds. i'll leave it at that.

just cuz its a nk275 is meaningless. and i am fairly sure there's chinese knockoffs of them starting to show up.

anyways, sorry fot the rambling reply. i would start by calling mike piera at analog man and explain the issue, and see what he says. if he offers to repair the pedal, that's cool. if he wants money? @#$% that. do it yourself.

odds are, it will work fine on the bench, mike's about 60 miles away in bethel, ct. we have similar climate. CT is a bad place to bias germanium. shit changes too much. fuzz faces are like new england weather. if ya don't like it, wait 5 minutes and it will be different

just outta curiousity, could the sun dial pot have smoked? that could account for weirdness, too. sometimes the track will burn thru if the associated q goes into runaway and draws too much current.  i don't like the way these things bias with that circuit too much, but i'm looking for a more versatile fuzztone usually.

and then tell your bud perhaps he'd be better paying YOU a bit less $$ for actual hand-built boutique stuff and having money left over for a sack of whatever vegetation one may prefer.