(SOLVED) 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.

 

[Locrian99]

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.

I feel like i have quite a few pedals that are like that. I rare have any of my volume knobs up much at all of the gain/drive knob is high. Any fuzz face/tone bender pedal (which if in remembering right this is in that vain.) thats kind of how the fuzz knob works ime. Its why one knob fuzzes are a thing. Because its going to be at max anyways.

 

[jwin615]

As @Locrian99 said, pretty typical.
Cascaded gain stages will be loud. This is also beneficial for pushing an amp's input.
You can easily manipulate the pot without removal. Easier to tack a resistor on rather than desolder the pot.
Here's a good read regarding that:

The Secret Life of Pots

 

[Mcknib]

From your symptoms it does sound like you've mixed the pot values up

When you checked their values was it across the 2 outer lugs

I can't see where you've soldered your green SW wire to but it looks to me like you'd want to solder to the top pad of the 3PDT clr

Check to see if the red circles have continuity if so solder SW to the top clr pad your SW connection on the main pcb connects R100 to ground via the 3PDT switching it on, so as long as your LED polarity is correct it should work

Obviously if the 2 red circles have continuity and bitches wire their 3PDTs the same

 

[SurfaceDweller]

As @Locrian99 said, pretty typical.
Cascaded gain stages will be loud. This is also beneficial for pushing an amp's input.
You can easily manipulate the pot without removal. Easier to tack a resistor on rather than desolder the pot.
Here's a good read regarding that:

The Secret Life of Pots

Awesome, thanks for the link. I'm going to try the resistor trick, I was scratching my head trying to figure out how I would desolder 3 prongs simultaneously.

 

[jwin615]

Awesome, thanks for the link. I'm going to try the resistor trick, I was scratching my head trying to figure out how I would desolder 3 prongs simultaneously.

You can bend the pots up 15° or so to check the value. But only do it once.
If you bridge resistors, use the pressfit holes where the legs meet the body.

 

[SurfaceDweller]

You can bend the pots up 15° or so to check the value. But only do it once.
If you bridge resistors, use the pressfit holes where the legs meet the body.

I'm confused, I've been playing around with different resistors in parallel w/ the volume pot (A100K), and I can't seem to increase the resistance of the pot, only decrease it. I've used 47k and 1M resistors so far.

Don't I need to increase the resistance of the pot to decrease the volume output?

 

[spi]

I'm confused, I've been playing around with different resistors in parallel w/ the volume pot (A100K), and I can't seem to increase the resistance of the pot, only decrease it. I've used 47k and 1M resistors so far.

You can't. The most resistance you'll get by putting two resistors in parallel is the resistance of the lesser of the two.

You can change the taper though. Lowering the resistance shouldn't have that much (if any) impact on the volume output--the volume pot is just acting as a voltage divider, regardless of its size.