Debugging my Fuzz Face

[FiddlerTheDrum]

I've been working on a re-house + LED/9v adaptor for my Fuzz Face (first project!)

As I am finishing things up, I am having problems getting any signal when the circuit is on. After checking continuity, grounding, the type of steps outlined in debugging, I made an audio probe and started poking around.

I have good signal up until the collector of my 8.2k resistor, but barely any audio comes through the other side of the 8.2k resistor. This same low level of signal continues through to volume pot, switch, and output jack.

I have not done any soldering on that resistor for this project. Should I suspect that the resistor could be bad? I suppose I could unsolder a leg and check as the next step. I've been chasing all sorts of gremlins on this project as I'm super new but having fun. I definitely had the switch wired incorrectly at first but I think I got that sorted, though I hope I didn't fry something along the way....

[duck_arse]

hello FiddlerTheDrum, welcome aboard.

photos. please show us photos of what you have bilt [don't make us come after you!] everytime. and voltages, measure your transistor voltages and post them here. and the circuit diagram - always always always always always, even if it is a fuzzface, post the circuit of what you are building in the thread. really, don't make us come after you for circuit diagrams, we get nasty.

and circuit diagrams are different to layout diagrams. any questions about method, just ask, or we'll come after you.

[Marcos - Munky]

Welcome!

As Duck said, photos will help a lot to see what you've done.

Good thing you know how to do an audio probe test, and already found out where is the signal going weak. The 8k2 resistor is at the output of the circuit, and also sets the bias voltage for the 2nd transistor. A resistor won't just go bad, so my bet it is a power issue.

Check again your 9V adaptor wiring, did you wired it correctly? Also, what transistors you have on your Fuzz Face? If they're PNP, the ground is positive, so you have to wire the dc jack in reverse polarity and also can't use the power supply to daisy-chain connect other pedals.

[iainpunk]

that resistor does what its supposed to do, lower the volume.
i'd say move the cap that goes from the volume pot to the other side of the 8.2k resistor, this gives way more output volume than it was designed to.
the other option is enlarging the other resistor (470 ohm) to 1k.

cheers

*originally, the engineers were ''afraid'' of over-driving the tubes in the amp for some reason, that's why that volume dropper is designed in to the original unit. i think that in the age of over-driving the front end of amps, that feature is redundant.

[GibsonGM]

*originally, the engineers were ''afraid'' of over-driving the tubes in the amp for some reason, that's why that volume dropper is designed in to the original unit. i think that in the age of over-driving the front end of amps, that feature is redundant.

I wonder if the reason for that thinking back then could've been to 'avoid blocking distortion' due to too-large bypass caps, no grid stoppers and things like that?  Just a thought, might have nothing to do with it, and no issue today.

[FiddlerTheDrum]

Circuit complete with my chicken scratch as I've been learning. I was comparing my voltages to electro smash website. The voltage between Q1 and Q2 looks out of whack, -5.04v? Same with between the 2.2uf cap and Q1.

The LED also doesn't turn on though it is getting voltage. Decent chance I fried it soldering it since I didn't know what I was doing. However, wouldn't the circuit still work even without the LED since the board is getting voltage and is connected to ground? Please stop me if you can tell I don't know what I'm doing haha

[FiddlerTheDrum]

Welcome!

As Duck said, photos will help a lot to see what you've done.

Good thing you know how to do an audio probe test, and already found out where is the signal going weak. The 8k2 resistor is at the output of the circuit, and also sets the bias voltage for the 2nd transistor. A resistor won't just go bad, so my bet it is a power issue.

Check again your 9V adaptor wiring, did you wired it correctly? Also, what transistors you have on your Fuzz Face? If they're PNP, the ground is positive, so you have to wire the dc jack in reverse polarity and also can't use the power supply to daisy-chain connect other pedals.

This is PNP. It started it's life as a 90s Dunlop, had Analogman mod it in 2002 for the "68 mod" whatever that meant (I was young then, my memory has failed me), and now I'm chopping it up for fun and science.

I flipped the DC power and I will be using with a Strymon Zuma w/ reverse polarity cable

[GibsonGM]

If it's wired as it looks, true bypass and without some crazy scheme to it, then the LED would be on separate switch contacts, so yes it should not be part of 'why it won't work'.

Can you post transistor voltages?

[FiddlerTheDrum]

Hi, I got fairly sidetracked with other life happenings!

Q1: Collector 4.89; Base 4.74; Emitter 0
Q2: Collector 5.03; Base 4.89; Emitter 0.39

[FiddlerTheDrum]

And I guess to be clear, those are negative voltages.

The one that is really weird is the Q1 base. That one should be closer to -0.2v from what I've been looking at.

Could a fried Q1 cause voltages like this?