Troubleshooting a Fuzz Face Clone

Started by Spidermonkey, November 21, 2009, 08:48:06 PM

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Spidermonkey

I'm building a fuzz face clone from this site- http://aronnelson.com/gallery/main.php/v/DRAGONFLY-LAYOUTS_0/album18/FUZZ+PCB/VINTAGE+STYLE+FUZZ+FACE+-+SILICON_001.GIF.html
I've finished, and the bypass works fine, the led lights up fine, but there is absolutely no sound from the pedal when engaged.
I have added a voltage divider pot, simulating a dying battery effect, and an LED.
My voltages are: Out of circuit battery= 9.91V Voltage at the circuit board end of the red battery lead = 9.84V

Q1
C = 0.29
B = 0.7
E = 0

Q2
C= 9.77
B=  0.3
E= 0.02

This is my first build, and first try at perf, so it's real messy, but I'm almost positive that I have no bridges. Here's a picture of my board-

Any help would be appreciated. Thanks!


petemoore

Convention creates following, following creates convention.

Spidermonkey

I know, I have those connected. Could the problem be the added LED? If so, how would I go about wiring a 3PDT switch without an LED? I've looked and can't find a diagram online.
Thanks

petemoore

Q1
C = 0.29
B = 0.7
E = 0

Q2
C= 9.77
B=  0.3
E= 0.02
  Must be a misread, if connected they'd be the same V.
  The LED circuit [using typical 3pdt switch] is a separate circuit from the audio circuit.
  The LED would be the LED, it's current limiting resistor so it doesn't burn up, and two poles of the switch that aren't used for bypass or effect switching, a separate 'column' of a pole and two throws, not the bypass side but the effect side, and the pole [in the middle] are used to break the power supply circuit, V+ and usually ground is switched [lifted] in the 3PDT.
  Hook the LED and resistor to the power supply the right way around and it'll light, the unassigned '3rd column' is used to make/break the LED circuit.
Convention creates following, following creates convention.

Spidermonkey

Okay, thanks for the info. Q1C and Q2B are in fact connected, it's just that my mulitmeter is cheap and a little jumpy. I'll keep poking around and try to find something that's wrong.

petemoore

  Cheep meters, what I use too.
  Something's letting Q2C 'ride up' near V+, could be not enough collector resistor value or something else isn't ''pulling down'' on it to keep it nearer 1/2v bias [about 4.5v or 5v].
  Measure every resistor value [distant point... [patented], find a point which should have 'X' resistance on it which is farthest away, test all connections between at the same time !]
  Count the # of connections at each node, compare schematic to the board using DMM measurements if possible, close in-light and magnifying glass doesn't always tell the full story like the DMM does.
Convention creates following, following creates convention.

Spidermonkey

Hmm. The resistance measurement from Q2C to the voltage input is 8.5K, as it should be from the schematic, and the resistors are all wired up alright. In the schematic, the voltage goes directly from V+ in, through R2 (330R) and R3 (8.2K) to Q2c. Why would the voltage be around 4.5V? I'm new at electronics, so if this is a dumb question, I apologize.

petemoore

Why would the voltage be around 4.5V? I'm new at electronics, so if this is a dumb question, I apologize.
  I'd just say it's too general, she [Mother Nature] deals with general stuff, but only when every specific condition has been accomodated perfectly, and is in place.
  Simple answer that doesn't find out why is:
  Either something is pulling it up or something should be pulling the voltage down but isn't.
  Q2e to ground resistance ?
  And total resistance from Q2c to V+ looks like R2 + R3 ?
  Q1C to V+.
  What is the voltage of Q1c / Q2b ?
  Any stray...anything...or ground where it shouldn't be on the board.
  Choose ''node 1'' [pick a node], verify with the DMM that everything and only everything shown to connect at that node 'beeps', and that nothing else beeps...or shows an odd resistance.
Convention creates following, following creates convention.

Spidermonkey

As far as I can tell, there is nothing stray that could be shorting or anything, and all of my checks with resistances have been consistent with the schematic. Here are the values you asked about-
Q2e to ground resistance ? - 8.52K
And total resistance from Q2c to V+ looks like R2 + R3 ? Yes indeed; 8.52K
Q1C to V+. - 32.8K
What is the voltage of Q1c / Q2b ? - 0.28V

Spidermonkey

Hey, thanks for the advice. As I was going to take pictures to post, I saw a discrepancy! I had accidentally connected my lug 3 of Fuzz to Q2B instead of Q2C. I switched it back, and it works perfectly! Thanks again for all the help.

petemoore

  We can thank RG !
  Electronics is a funny thing, by the time schematic, board and everything else is happeneing it's really easiest for the person with them there to see 'em, I literally can't see 'em.
  Every mark on the schematic depicts a state of circumstance, she has electrons searching for them at all times, they never change.
  Often enough we're able to discover the circumstances which allow control of the electrons to make them do what we will them to.
Convention creates following, following creates convention.