Parentheses Fuzz: Distortion switch kills the signal.

[clipped_diode]

Click here to see the "completed" build outside of an enclosure.

I've only done three kits before sourcing parts for this PCB, so I'm still relatively new to DIY pedals. I expected some trouble from the finished pedal because throughout the build several pads popped off and the copper plate is slightly exposed in a few spots. (Ultimately, I don't think the pads caused a problem because in each instance at least one side still had a pad.)

I am using an audio signal probe to diagnose. This post is probably a little premature because I'm still trying to understand the schematic, but here's what I know right now.

1. True bypass works.
2. The effect seems to work. I get a heavy distortion (almost 8-bit velcro ) and an octave sound. I'm not sure how much this pedal is meant to clean up but even with distortion all the way off it is still heavily distorted. EDIT: Playing with a guitar it is clear that this is way more "gated" sounding than it should be. I have to strum HARD for a short spike of sound that quickly falls off. (Like velcro settings on Fuzz Factory or similar.)
3. Turning the octave knob down lowers the total output volume.
4. If I switch the octave switch, the output dies.
5. If I switch the boost switch, the output dies.

I don't have LEDs installed so it's not clear if the sound dies when I engage or disengage the switches. I assume the octave OFF kills the sound because I can hear an octave otherwise. It's not clear to me if the boost is ON or OFF however.

EDIT: Updated title to reflect current issue. It's the distortion switch that kills the signal. Octave switch does nothing. I got the boost side working after replacing a part.

 

[clipped_diode]

That's good. The resistance is off the scale, as it should be. See if any of the other pins on IC1 read resistance to ground.

Pin 1: No reading
Pin 2: No reading
Pin 3: 1M
Pin 4: Ground
Pin 5: No reading
Pin 6: No reading
Pin 7: 3.7K and climbing fast
Pin 8: No reading

Then measure the resistance between pis 2 & 6 with the distortion pot at zero, noon & max. Those measurements should be 0 Ohms, 15K and 100K, more-or-less.

Pin 2 to 6 at zero: No reading
Pin 2 to 6 at noon: No reading
Pin 2 to 6 at max: No reading

Does the pedal need power for this test?

One more resistance measurement: pin 1 to pin 8. Should be off the scale.

Pin 1 to 8: No reading

 

[Chuck D. Bones]

Power should be off for the entire test. Your readings point to a problem with the DISTORTION pot. It's either broken or one of the traces to it is broken.

We're almost there.

Measure from IC1 pin 2 to pin 3 of the DISTORTION pot.
Measure from IC1 pin 6 to pin 1 of the DISTORTION pot.
Measure from pin 1 to pin 3 on the DISTORTION pot.

Just to be clear, pin 1 on the DISTORTION pot has a square pad.

At least one of those measurements will read off the scale.

 

[clipped_diode]

Measure from IC1 pin 2 to pin 3 of the DISTORTION pot.

No reading.

Measure from IC1 pin 6 to pin 1 of the DISTORTION pot.

0.2R

Measure from pin 1 to pin 3 on the DISTORTION pot.

92 K cranked.

 

[Chuck D. Bones]

Are you measuring on the pot or on the circuit board pads where the wires to the pot are soldered? Time for some visual inspection. Look for a bad or missing solder joint on pin 3 of the DISTORTION pot (both ends of the purple wire) or a cracked trace. Look on both sides of the board. Did you happen to remove and replace C15?

 

[clipped_diode]

Are you measuring on the pot or on the circuit board pads where the wires to the pot are soldered? Time for some visual inspection. Look for a bad or missing solder joint on pin 3 of the DISTORTION pot (both ends of the purple wire) or a cracked trace. Look on both sides of the board. Did you happen to remove and replace C15?

Those measurements are at the PCB joints for the respective pot lugs. I get the same readings if I test at the actual lugs.

Here's what the area looks like (super high res). The distortion pot is at the top-middle. I can try reflowing again.

https://imgur.com/gk8ivH2

https://imgur.com/1AXFasg

 

[Chuck D. Bones]

Does your meter auto-range? You should be getting 100K when you measure from pin 1 to pin 3 right at the pot. If it reads off-scale there, then either the meter is on the wrong resistance range or that pot is toast.

 

[clipped_diode]

Does your meter auto-range? You should be getting 100K when you measure from pin 1 to pin 3 right at the pot. If it reads off-scale there, then either the meter is on the wrong resistance range or that pot is toast.

I was wrong. From lug 1 to lug 3 it's 92+K when the pot is cranked. It's responsive to turns of the pot. I measured from the IC before. The meter does auto range.

 

[Nostradoomus]

 

[clipped_diode]

Should I be hearing audio out of more IC pins? How come I can't hear it leaving pin 2 and going to the pot? I do hear it at lug 1 and 2 of the pot, it's just completely gated and blown out — even at lug 2, which I think should be relatively clean.

 

[Chuck D. Bones]

When it's working right, which it isn't right now, you should hear the same thing on pins 2 & 3. Pin 6 should be louder and clean with low DISTORTION settings, getting dirty at higher DISTORTION settings. Probing pins 1 & 8 aren't that useful. There will be signal on both of them, with pin 8 being louder. There is a break somewhere between IC1-2 and DISTORTION pin 3. Measure resistance from IC1-2 to the pad for DISTORTION pin 3. Then from the pad for DISTORTION pin 3 to the actual pot pin 3. One of those measurements will be high resistance, the break is somewhere between those two points. Inspect, reflow, and retest with the meter until it's low resistance from the IC to the pot.

What's that white wire doing on IC1-2?

 

[clipped_diode]

When it's working right, which it isn't right now, you should hear the same thing on pins 2 & 3. Pin 6 should be louder and clean with low DISTORTION settings, getting dirty at higher DISTORTION settings. Probing pins 1 & 8 aren't that useful. There will be signal on both of them, with pin 8 being louder.

What's that white wire doing on IC1-2?

Here are details of what I am hearing out of IC1. The white wires represent my attempts at making sure the connection from pin 2 > C11 > pin 6 highlighted below is made. One of the pads looked broken to me, so I directly wired it. The post linked at the beginning of this paragraph has photos of the wiring. Did I screw it up?

There is a break somewhere between IC1-2 and DISTORTION pin 3. Measure resistance from IC1-2 to the pad for DISTORTION pin 3. Then from the pad for DISTORTION pin 3 to the actual pot pin 3. One of those measurements will be high resistance, the break is somewhere between those two points. Inspect, reflow, and retest with the meter until it's low resistance from the IC to the pot.

IC1-2 to DIST 3 pad: No reading
DIST 3 pad to DIST 3 lug: 0.1 R.

 

[Chuck D. Bones]

It's important that any wire connected to pin 2 is short as possible and lays down on the board so it doesn't act like an antenna. This is a long thread so please forgive me if I go back over something that was already discussed. Typical trace repairs are done with 28 or 30 AWG solid wire and have the shortest span possible. It would appear that your pin 2 trace repair did not repair all of the broken paths because the connection to the DISTORTION pot is not there. I use 30AWG wire-wrap wire for tiny jumpers and trace repair. Get some smaller solid wire and run a wire from IC1-2 to C11 and to the DISTORTION pot pad 3. Run the wires on the solder side of the board and keep them short. After you've done that, verify that IC1-2 connects to all of these places:
DISTORTION pad 3
R21
R22
C11

 

[clipped_diode]

It's important that any wire connected to pin 2 is short as possible and lays down on the board so it doesn't act like an antenna. This is a long thread so please forgive me if I go back over something that was already discussed. Typical trace repairs are done with 28 or 30 AWG solid wire and have the shortest span possible. It would appear that your pin 2 trace repair did not repair all of the broken paths because the connection to the DISTORTION pot is not there. I use 30AWG wire-wrap wire for tiny jumpers and trace repair. Get some smaller solid wire and run a wire from IC1-2 to C11 and to the DISTORTION pot pad 3. Run the wires on the solder side of the board and keep them short. After you've done that, verify that IC1-2 connects to all of these places:
DISTORTION pad 3
R21
R22
C11

Thanks so much for sticking with me. I did what you suggested and connected IC1-2 to DIST pad 3, and now I believe the pedal is functioning as it should. I don't know why I didn't consider wiring the pot in just like I did the C11 capacitor. I used 24 AWG wire but I may replace it before boxing it up.

Thanks again to everyone that helped! Cool sounding pedal.

 

[Chuck D. Bones]

Do us a solid and look in the General Questions forum for the topic "Parentheses - a show of hands." Please vote what happened to you, I'm keeping score.