Debugging: Woolly Mammoth

[elenore19]

DEBUGGGING
Name: Zvex Woolly Mammoth Clone
I built this pedal 2 years ago and it just recently stopped working. I don't remember the exact layout I used but this one looks like it has to be it. http://elkit.web.id/2011/04/zvex-woolly-mammoth-zvex-effects/
Exactly to spec layout wise.
Mods: I might have a different value resistor somewhere in it but honestly I don't remember at all. Nothing drastic.

It worked really well. It's my cleanest build I ever had. Then all of the sudden it just quit out. No sound AT ALL. Made me think a ground @#$%ing up somewhere—Checked all obvious connections (at least to me) and everything seemed legit. So now I'm here, needing to fix this before the owner of the pedal wants a refund!

Measurements:
Using this orientation on the transistors--http://web.tiscali.it/chipperia/components/to92-cbe.gif

Q1
C - .927v
B - 1.563v
E - .955v

Q2
C - 0v
B - .628v
E – 1.561v

Thanks for the help!

-Elliot

Pictures: Taken with a desktop cam so really not the best.

[PRR]

It was good to mention that it DID work. This eliminates many new-build questions.

Your voltages are SO wrong that I am sure you have the E-B-C wrong.

Or you mixed Q1 and Q2??

We know that Q1 C and Q2 B are connected together, and should have the same voltage; you show Q1 B same-as Q2 E.

Since it DID work, the build is right, your readings are mixed. I have annotated the layout with pin-names below.

You also do not show any "high" voltage anywhere. We'd expect Q2 C to be several volts; but you don't have over 1.6V anywhere. And some suspicious same-voltage readings. I suspect power is not flowing from +9V to Q2. Look for a flaw along the yellow dotted path (Q2 C to R5,R5 to +9V).

[Kipper4]

I must have read your voltages wrong too. Since you put a point before like so .927 I assumed it was less than a volt.
and as PPR says Q1 C should be the same voltage as Q2 B.
Now I'm confused.

[elenore19]

Yeah I had them switched. Sorry 

Not really sure what to look for along the dotted path. I checked connectivity and everything checked out there. I tried to check the ohms on the resistor thinking that was it but that didn't work.. I decided it made sense because, correct me if I'm wrong, would be trying to measure the resistance of every other chain of parts that also connect the two locations (?). How else do I check the resistor? Just replace it? Or would there be another thing to check? Thanks so much for the help--first time I've really had to debug..

[PRR]

> Yeah I had them switched. Sorry

WHAT "switched"? The transistors? The leads? BOTH?

It still is not making sense, and I don't care to work out the 12 different ways two sets of three legs can be "switched" to try to find the least-preposterous combination.

Please post the voltages using the part and leg designations in my image.

But my 2 cents is still on a bad solder joint. Hangs-in for a day, a week.... I saw one hang-in for a decade and then let-go, let a lot of smoke out (wasn't a pedal).

[elenore19]

> Yeah I had them switched. Sorry

WHAT "switched"? The transistors? The leads? BOTH?

The way I posted them.. Same readings only instead of these:
Q1
C - .927v
B - 1.563v
E - .955v

Q2
C - 0v
B - .628v
E – 1.561v

The right way to label them would be
Q1
E - .927v
B - 1.563v
C - .955v

Q2
E - 0v
B - .628v
C - 1.561v

I'll resolder everything in that yellow path that was posted before and hopefully it'll work. Thanks for all the help!

[PRR]

> Q2
> E - 0v
> B - .628v
> E - 1.561v

Q2 has two E and no C?

[elenore19]

> Q2
> E - 0v
> B - .628v
> E - 1.561v

Q2 has two E and no C?

Mistyped. Fixed.
Q2
E - 0v
B - .628v
C - 1.561v

Resoldered all joints in yellow path still no voltages over 1.6v. I might try and replace the resistor to see what happens.

[PRR]

This still does not make sense. Q1B connects to Q2C? Q2E connects to zero V?

I hate to harp on this, but solving such problems when the data is mixed-up is like doing a crossword puzzle with the ACROSS and DOWN swapped.

Obviously, despite my little picture, you have Q1 and Q2 confused.

This still leads to the path shown in yellow-dots. _Q2_ C should be pulled-up to something like half of 9V; instead it shows a trace less than Q2 E which means no current is getting to Q2 C through that 20K resistor.

A failed resistor is incredibly rare but I suppose it is cheap to try.

[elenore19]

This still does not make sense. Q1B connects to Q2C? Q2E connects to zero V?

I hate to harp on this, but solving such problems when the data is mixed-up is like doing a crossword puzzle with the ACROSS and DOWN swapped.

Obviously, despite my little picture, you have Q1 and Q2 confused.

This still leads to the path shown in yellow-dots. _Q2_ C should be pulled-up to something like half of 9V; instead it shows a trace less than Q2 E which means no current is getting to Q2 C through that 20K resistor.

A failed resistor is incredibly rare but I suppose it is cheap to try.

No worries on the harping. I feel like an idiot for not already figuring it out. Okay I think I just have Q1 & Q2 mixed up. If that doesn't make sense I really start to rethink my life

Right, the voltage is too low. All I did with the joints was heat them up and essentially "remelted" them--or resoldered them is what I called it. Is that the correct way to do that? Or should I try and remove all the solder and then get new solder in there. e

[akalabeth]

I'm having exactly the same problem on a Vero Wooly Mammoth.

Q1
E 0.0v
B 0.20V
C 1.70V

Q2
E 1.03V
B 1.69V
C 1.05V

@OP Did you made it work?

Thanks in advance.

[PRR]

> Q1 B 0.20V
> Q2 E 1.03V

Short the Pinch pot. Does Q1 B come up above a half-volt?

[akalabeth]

> Q1 B 0.20V
> Q2 E 1.03V

Short the Pinch pot. Does Q1 B come up above a half-volt?

PRR. Thanks for the reply

I got the same readings for everything, except Q1 B: 0,15V

I already replaced all the caps and transistors. Triple checked orientations and ground connections. Checked every slug/lead connections with the copper traces.
The only difference of the original schematic is that I replaced Fuzz/Wool pot (2k) with a 5k. (read on a forum that it doesn't mess up)

Should I replace the R3 (51k) and R5 (20k) coming from the 9V?

I love electronic as a hobby, but my lack of knowledge is frustrating sometimes.

[akalabeth]

After quadchecking everything I found that bite(pinch) lugs 2,3 and the C3 had a gap between Q2 and R4.
My mistake while drawing the traces from the veroboard to a pcb (I did it by hand)

Thank you again, everything working.
My mistake