Troubleshooting: Madbean Pastyface (Tonebender/Soulbender) Not Fuzzing

[afrogoose]

Hi Everyone,

I've just finished my Pastyface build (tone bender).  I'm having some trouble though.  It's not really fuzzing out.  Even with the fuzz knob cranked and the internal trimmer maxed out there's really no clipping.  When the fuzz knob is below halfway there is no output.  The volume and tone pots seem to be working as expected.  Here are my voltages.  The IC voltages look good but the GE trannies look all wrong.

IC:
1. 9.2
2. 5.43
3. 0
4. -3.72
5. -9.14
6. 4.38
7. 5.77
8. 9.2

Q1
C  -.14
B  -.22
E  -.13

Q2
C  -.14
B  -.13
E  -.14

Q3
C  -.63
B  -.1
E.  0

I'm pretty stuck.  I've tried different transistors with the same results.  Does anyone have any suggestion on what's gone wrong??

I appreciate any insight/help anyone has!!!  Thank you in advance!!

[MikeA]

You've got -9V leaving pin 5 of IC1, but it's not going very far.  None of the transistors are getting any of it.  Looks like pin 5 is not making contact with the trace on the PCB.  If IC1 is socketed, take it out and check continuity from the pin 5 socket to the PCB, then to R3, R4 and R12 (probably bad socket or bad solder joint on pin 5).  If it's not socketed, check your soldering on that pin.   Mike

[afrogoose]

Hey Mike!

Thanks for the quick reply! The IC is soldered and all the joints look good.  Also, I have continuity between pin 5 and R3, R4, and R12 as well.

Do you have any other suggestions?

Thanks!!

[willienillie]

https://www.madbeanpedals.com/projects/_folders/Classics/pdf/Pastyface2020.pdf

[MikeA]

So with power on, check the voltage on the -9V bus at each point from pin 5 of the IC, through those 3 resistors, to the transistors.  The schematic in the build doc will show you the test points.  Somewhere it's dropping from -9V to -0.14V, which tells me it's open.

[afrogoose]

Thanks again Mike for the good advice.  It turns out I had the wrong value for one of the resistors.  Instead of a 3K3 for R6 I had like a 33K or 330 or something like that.  Not sure if I sourced the wrong part or if Mouser just made a mistake.  I would think I would have caught that kind of thing when I was pulling the resistor out of the bag but it's probably my fault.  I'm not that quick with resistor codes so I wouldn't know the value without looking it up anyway.

So the pedal works great and sounds great now.  Thanks again for all the help!!

[MikeA]

Congratulations!  I've done the same, including substituting a 47k for a 4.7k...  Now I measure everything before it goes in, saves troubleshooting time later.