My pedal died... Crap!

[StevenJM]

I tried both ... battery and 9v adapter.  Same results.   I'm gonna have to read through that audio probe idea again, I got a little lost reading through it.

What sound am I looking for when I'm touching parts?  Just a buzz?

[newfish]

I tried both ... battery and 9v adapter.  Same results.   I'm gonna have to read through that audio probe idea again, I got a little lost reading through it.

What sound am I looking for when I'm touching parts?  Just a buzz?

The audio probe allows you to 'listen' to each stage in turn.  Think of it as a 'circuit stethoscope'.

You should be able to find the point at which the audio signal is lost in your pedal - and then drill down to find out why.

The first couple of de-bugs are a PITA, but you *do* learn from them. 

Hang in there.

[StevenJM]

if I buy a multimeter with the continuity tester, thats basically the same idea, right?

[GGBB]

Not the same.  The audio probe lets you tap in to the circuit and actually listen to the guitar signal through your amp at any point in the circuit's audio path.

[StevenJM]

I'm so confused by this issue.  I got it so the light will turn on, but then fades away right away.  I'll try a different battery.

I need to buy a capacitor so I can try the audio probe.  None of my electrolytic caps look damaged... And I went thru the board with a continuity tester and it seemed like all my parts were passing a signal.  (it was kind of a pain using that thing)... Something is definitely screwing with me.

[LucifersTrip]

The thread's gone on too long without the most important things from the debug thread....the schematic, subs (if any) and voltages

http://www.diystompboxes.com/smfforum/index.php?topic=29816.0

If you don't understand how to take them (multimeter required), someone will help

[StevenJM]

I have off tomorrow, I'm going to menards first thing in the morning and getting a multimeter.  Ill probably have a handful of questions on using it... I've used one to read ohms of a speaker and guitar parts but never a circuit board.  I was hoping this would be an easy swap of a part and it'd be working... But I'm kind of glad it didnt fix it just so I can learn how to do the troubleshooting.

[LucifersTrip]

  I was hoping this would be an easy swap of a part and it'd be working...

It probably will be, but multimeters and audio probes pinpoint

[Paul Marossy]

I should add that an audio probe is only good if you know how to follow the signal path on a schematic and translate that to a real world circuit. If you can't do that, it's not going to be much help...

[StevenJM]

First off... the LED issue was due to a battery issue, so i grabbed a different battery and the LED works fine now.

Schematic:

http://www.generalguitargadgets.com/pdf/ggg_secf_sc_bst.pdf?phpMyAdmin=78482479fd7e7fc3768044a841b3e85a

The battery reads out at 9.04v so its a fresh battery... these are the results I got...

Q1
C=8.93
B=0.01
E=0.00

Q2
C=3.41
B=0.60
E=0.00

Q3
C=6.03
B=0.71
E=0.12

D1
A=0.00
K=9.19

Anything funny stand out to ya guys?

[LucifersTrip]

the led should've lit with a dead battery...you only need 2-3v, i believe...

if you checked out the build instructions on the GGG site
http://www.generalguitargadgets.com/projects/73-fuzz-tones/89-shin-ei-companion-fuzz
"Shin Ei Companion Fuzz Build Instructions"

...then, you can see Q1C is the most off. your collector is near the supply voltage (9v), which it should not be. i'd check components around that area first

from ggg:
===
Component Location Voltage
9 volt power supply 8.8v
Q1 Collector 6.6v
Base 0.6v
Emitter 0v
Q2 Collector 2.0v
Base 0.6v
Emitter 0v
Q3 Collector 6.6v
Base 0.7v
Emitter 0.1v
===

the fact that you have 6v on Q3C and the output comes right off that leads me to believe you should be getting some sound. what do you get now?

did you check the 10uf at the output?

[StevenJM]

the led should've lit with a dead battery...you only need 2-3v, i believe...

if you checked out the build instructions on the GGG site
http://www.generalguitargadgets.com/projects/73-fuzz-tones/89-shin-ei-companion-fuzz
"Shin Ei Companion Fuzz Build Instructions"

...then, you can see Q1C is the most off. your collector is near the supply voltage (9v), which it should not be. i'd check components around that area first

from ggg:
===
Component Location Voltage
9 volt power supply 8.8v
Q1 Collector 6.6v
Base 0.6v
Emitter 0v
Q2 Collector 2.0v
Base 0.6v
Emitter 0v
Q3 Collector 6.6v
Base 0.7v
Emitter 0.1v
===

the fact that you have 6v on Q3C and the output comes right off that leads me to believe you should be getting some sound. what do you get now?

did you check the 10uf at the output?

The last battery had some damage to the negative snap, so the battery clip wasn't sitting in snug, resulting in the LED issue...

I'm not sure why that Transistor is running so high. 

I tested the last 10uf cap, right before the output of the board and thats giving me a 6.08v reading too, the same as the C of Q3.

[StevenJM]

My 22K resistor before Q1 doesn't really seem to be resisting much power.  The reading on one end is 8.98 and the other end (leading to Q1) is 8.70. 

But still, now i'm questioning if its something off-board thats my issue.  all my wiring LOOKS fine... and the pedal was working fine for months, and minutes before it stopped working. 

I feel like i'm close, but i also feel like throwing this thing against a brick wall.

[StevenJM]

So i made a little audio probe... and i get sound all the way up to the base of Q1, but anywhere I go from there i just get a shock-like noise but no sound.  But I also get a huge volume drop going from one side of the .047uf to the other side of the cap, right after the input.  Is that normal? 

[LucifersTrip]

from the audio probe & voltage info, I would start by replacing Q1

[StevenJM]

q1 and q2 i think might need to be replaced...

I'm not sure whats different now compared to a few hours ago... but now i'm getting even more ridiculous numbers for Q2.

But this is what i'm getting while typing this...

Q2 (GGG's readings in parenthesis)
C=7.66 (2.0)
B=3.74 (0.6)
E=0.00 (0.0)

I've been unsoldering/resoldering everything trying to get this thing to work and nothing... theres only so many parts to this thing, it shouldn't be this much trouble. 

[StevenJM]

out of frustration i decided to put in new transistors just now.  I had some spare 2N3904 so I put them in place of the 2N2369s and this what I've got now...

Q1 (GGG)
C=2.43 (6.6)
B=0.58 (0.6)
E=0.0 (0.0)

Q2 (GGG)
C=0.84(2.0)
B=0.54 (0.6)
E=0.0 (0.0)

So the numbers are still off, but now lower instead of higher than GGG's recommended readings... but I just plugged it in, and I've got fuzz again.  So i'm pretty relieved... i can go to bed now haha...

Hopefully the 2N3904s doesn't change the beast this fuzz was before it stopped working.  I used the 2n3904s in a fuzz rite clone a while back and liked the results so hopefully the same will apply here.

Thanks for everyone's help... i would've had no clue where to even start if it wasn't for the help here. 

Any other input on the numbers being off?  or is that normal for the type of transistor i have in there now?

[Paul Marossy]

So it seems to go back to what I suggested early on, that one or more the active components got damaged from an accidental reversal of the power supply polarity. That's not supposed to happen if there is a reverse polarity protection diode on the power supply of the circuit. Did you put that diode in your build StevenJM? Just curious...

[StevenJM]

I do have the diode in my circuit...

[Paul Marossy]

That's just weird. Seems like something that should have never happened.