Breadboarding a Fuzz-Rite...

[Coda]

Be lately been breadboarding. I started with the Small Bear Fuzz Face tutorial (Si), and have been messing around with that for a bit. After that, I build a Vox Tone Bender (Si), which follows the basic skeleton of the Fuzz Face, and adds a bit. I prefer the Tone Bender, and have been swapping out stuff on the Fuzz Face.
Today, I decided to try to breadboard the Mosrite Fuzz Face, from the schematic. I did my best, and ended up with a circuit that passes sound. However, that sound is pretty clean. No fuzz at all. I started with 2n3904’s, and even tried 5088’s (I have them in my PCB build, and like them)...clean with both.
I’m not expecting a complete resolution. I should probably try again with a different layout, but I thought I’d ask anyway. What might my issue be? I’ve attached a photo, but I doubt it’ll help much. Also, I am out of 470k resistors, so I used (or tried to use) 2 220k resistors in series. Maybe that’s he issue? Also, I’m out of B500k pots, and I substituted both a B250, and a C500k, with the same results. I also have the jacks and battery removed I’m this particular photo; input at B2, output at B25 ground on the side of the pots, power on top...

 

[dlazzarini]

I haven’t seen the schematic but just from looking at your pic, it doesn’t look like you have anything connected to on of the legs on the tranny at the bottom of the pic. It looks like your jumper missed it by one hole

 

[Coda]

I haven’t seen the schematic but just from looking at your pic, it doesn’t look like you have anything connected to on of the legs on the tranny at the bottom of the pic. It looks like your jumper missed it by one hole

Q1 base is at A7, and connects to the jumper at C7...or at least it’s supposed to. I’ll double check. Also, here’s the schematic used...

 

[Coda]

I haven’t seen the schematic but just from looking at your pic, it doesn’t look like you have anything connected to on of the legs on the tranny at the bottom of the pic. It looks like your jumper missed it by one hole

Ok. Following your suggestion, I traced back, and while the transistors are where they should be, I omitted a jumper. Between the 47n and the base of Q2. It fuzzes now...though it’s still far from 100% Fuzz-Rite. It sounds gated. Could the lack of B500k fuzz control be the issue? What about my Jerry-rigged 470k substitutes? Who is Jerry, anyway?...

 

[Chuck D. Bones]

What are the collector voltages?

 

[Coda]

What are the collector voltages?

Q1: .60, Q2: .01. Not looking too good...

Found a missed a jumper from the Q2 bias to power. Q2 reads .59 now.

 

[fig]

 

[fig]

Oh...you covered that....oops

I really should just read and keep my fingers shut...

 

[Chuck D. Bones]

Both transistors are near saturation. I don't know what the collector voltages are on a real Fuzz-Rite, but I'll hazard a guess and say they should be at least 2V. 4.5V would provide the most headroom and volume, but may not be the best tone. Only your ears will tell you that.

Options are:

1. Use transistors with lower hFE.
2. Increase The 470K resistors from base to collector.
3. Decrease the 470K resistors from collector to +9V.
4. Some combination of the above.

How about a better pic showing the current config? I'd like to help, but that low-res pic doesn't make it very easy...

 

[Coda]

I fixed it. I went back and re-traced everything out...I found a few blanks. I re-did a few parts, and boom: Fuzz-rite. Its classic Fuzz-Rite; buzzy, angry, metallic, and so on. This one sounds a bit louder than my pcb version. I also replaced my 2 series 220k resistors for a 150k and 330k in series. I feel that this has been a good learning experience. Thanks for all the help.