Posted by1 year ago
I just picked up a used Joe B fuzz face and the guy that sold it to me messed with the internal trim pots, if anyone has this pedal and knows the correct voltage for Q1 and Q2 or has a photo of the trim pots let me know. I think this pedal looks and sounds killer! I am glad i got one. Q2 emitter base current:.256 mA, giving an emitter voltage of -0.256 V The base voltage for Q1 should be slightly less or maybe about the same. Your base voltage is way too low to get Q1 to turn on. With it so close to zero, I'd suspect Q1 is shorted from base to emitter.
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I have a Seymour Duncan Tweak Fuzz. I was unable to find a schematic but it is a clone of the Dirty Boy Afro Fuzz, based on the Fuzz Face.
Here is a pic of the circuit.
Having no experience building pedals, I am modding this pedal as a first step to learn about DIY Pedal building and electronics in general. I've read on several forums for this pedal regarding swapping the R4 transistor with an 8k2 (8.2k?) and removing R5 and bridging it to increase the volume. A variation of this that I wanted to try was putting a 1K resistor in R4 and a trim pot in R5 to have an adjustable bias.
Here's my question, I currently have a 1k resistor in R4, I attempted to put a 10k trim pot in R5 (have removed it and jumped R5). I was looking for a bias of about 4.6 but I am not sure where I need to connect my meter leads to measure the Bias. I measured at Q1 (I've read that the Q1 and Q2 labels are swapped on the tweak fuzz) and it was reading between 9-14 volts as i swept the trim pot.
- Was this the correct way to measure the bias?
- Is the trim pot the wrong size?
- If i decide to scrap the trim pot, would you recommend keeping 1k in R4 and adding a 18K in R5 a la Hendrix/Mayer mod?
![Buy fuzz face Buy fuzz face](http://i.imgur.com/THTKv.png)
Update Luckily I live near a real deal electronics parts store and picked up a bunch of different resistor values. I put an 18k in R5 and measured the bias at Q1 (Q2 in most other FF derivatives) it was at 5.6V. I tested it with single coils and humbuckers and it sounds really good. Very tight fuzz and with the switchable caps can go to very thin to very wooly.
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