Help w/ Carbon Black Fuzz

[SurfaceDweller]

I'm working on a PedalPCB carbon black fuzz, and I screwed up the wiring somewhere. The pedal doesn't pass sound, even when bypassed, and when it is engaged there is a rhythmic "thumping" in time with the LED on my wall wart. The LED on the pedal doesn't light.

I've omitted the "top" control pot from the circuit and replaced it with a jumper. The circuit has a 2n222 in q1, and 2n222a for q2 and q3.

This is my 4th pedal build, and my first time using a breakout PCB for the foot switch. I own a cheap DMM but I'm not really sure how to troubleshoot the circuit. Thanks for your help!

 

[Stickman393]

Thumping with the LED on your wall wart makes me think that you've got a short somewhere in your pedal.

I'd measure voltage coming into the pedal to confirm. Maybe take a peek on the underside for solder bridges or little whiskers from your off board connections.

 

[SurfaceDweller]

It turns out I had the power jack wired up incorrectly.

Now that I've got the pedal up and running, I've found that the volume pot is extremely sensitive (unity is near the bottom of the dial), and all of the fuzz is at the very end of the fuzz pots travel. Is this typical for tonebender circuits, or does it sound like I've got my pots mixed up?

 

[jwin615]

It turns out I had the power jack wired up incorrectly.

Now that I've got the pedal up and running, I've found that the volume pot is extremely sensitive (unity is near the bottom of the dial), and all of the fuzz is at the very end of the fuzz pots travel. Is this typical for tonebender circuits, or does it sound like I've got my pots mixed up?

Possibly. You should be able to see the markings on the volume pot
Use your cell camera to zoom in if needed

 

[SurfaceDweller]

Possibly. You should be able to see the markings on the volume pot
Use your cell camera to zoom in if needed

There are no useful markings on these Alpha mini pots. I checked with the multimeter and they are the correct values.

It's odd that the volume control is super sensitive and the fuzz is only useful at the end of its sweep. I messed around with the bias control but it didn't change much. I'm glad the pedal works now at least!

 

[SurfaceDweller]

Bump.

Any idea what would cause the vol pot to be hyper sensitive, and the fuzz pot useless until the end of the sweep?

 

[BuddytheReow]

You could try swapping out the fuzz pot for a C-Taper and the volume pot for a B-Taper. You should have more control over the sweep that way.

 

[finebyfine]

Sounds like the 2n2222a's are installed backwards, if I'm remembering right the pinouts can vary by manufacturer

 

[jwin615]

CLR and LED on your 3pdt PCB needs to be jumpered for the LED to work. Though, I'm not certain that will work as I can't tell that it switches the SW pad, or keeps that row of the switch internal to the pcb.
If it still doesn't work, test the switch lugs to make sure they are switching. The center lug of each vertical row should switch to the top and bottom lug.

 

[spi]

CLR and LED on your 3pdt PCB needs to be jumpered for the LED to work. Though, I'm not certain that will work as I can't tell that it switches the SW pad, or keeps that row of the switch internal to the pcb.
If it still doesn't work, test the switch lugs to make sure they are switching. The center lug of each vertical row should switch to the top and bottom lug.

I've used that PCB before, and you're right--it needs you to jumper the CLR+LED.

 

[spi]

What kind of DC jack is that? I haven't seen one like it. Reason I ask is that some folks have had issues because the jack's outer ring makes contact with enclosure (i.e. not negative center).

 

[SurfaceDweller]

What kind of DC jack is that? I haven't seen one like it. Reason I ask is that some folks have had issues because the jack's outer ring makes contact with enclosure (i.e. not negative center).

My first issue was the DC jack being wired incorrectly, I replaced the foot switch prior to changing the jack.

The pedal works fine now, but the vol and fuzz pots are odd (see above posts).

 

[SurfaceDweller]

You could try swapping out the fuzz pot for a C-Taper and the volume pot for a B-Taper. You should have more control over the sweep that way.

Thanks, I might try this, especially for the volume pot. Unity volume is around 8 or 9 o' clock on the dial, it's wild.