NEED HELP Breadboarding a Silicon Fuzz Face Pedal

[bonzoboi]

Thanks for all of the recommendations! Also, sorry I haven't been able to get back to this until today, I only have time during the work week to work on this project.

So, I tested all of my components (resistors and capacitors) and everything is showing the correct values. Also, I've made that sure all of my cables work, as well as the guitar and amp I'm using to test this on, and that my battery has the correct voltage.

However, when I test from the tip of the input jack to the negative lead of the 2u2 input cap, as well as from the positive lead of the input cap to the base of Q1 and the 100K resistor (like GGBB recommended), I get a 0 V reading on the multimeter for both tests. I tested connectivity amongst the rest of the components on the board and I'm getting more positive voltage read outs from them; so, is the issue here maybe with the input jack and/or the 2u2 cap? Could it possibly be a soldering issue on the input jack?

[GGBB]

For that test you need to set your meter to resistance (or continuity if you have it), not voltage. You are looking for zero resistance (or a beep if using continuity) meaning that the components are connected as desired and therefore there are no bad connections anywhere due to the breadboard.

[bonzoboi]

@GGBB, oh okay gotcha! I'm still very new to this stuff so thank you for telling me that.

So, I set my meter to resistance, and was getting 0 ohm read outs between everything, except for between the first two measurements you recommended, as well as between the output jack tip and the 0.1 uf cap, where I was getting read-outs of about 0.5-0.7 ohms. Is this enough of a reading to suggest that there are some bad connections somewhere?

[GGBB]

Tiny resistances like that are not a problem. Infinite resistance would indicate no connection. Large resistance would indicate something wrong.

[bonzoboi]

I don't know if this is helpful to the troubleshooting process or not, but I tried testing with the multimeter when I have the guitar and amp plugged into my breadboard with the power on, and when I touch the right leg of the 0.1 uf cap (the leg that connects to the 500k pot) or to the tip of the output jack with the multimeter, my amp begins to buzz loudly, whereas when I am touching any of the other components on the board or nothing at all with the multimeter leads there is no sounds coming out of the amp. Could this indicate anything?

[thermionix]

Noises like that can be useful in troubleshooting.  You've started working your way backward through the circuit.  Seems like touching a meter probe the other leg of the .01 output cap might at least cause a light click sound to come through the amp.  The buzzing you describe could be related to DC output from the meter and DC would be blocked by the output cap.

I'm new to breadboarding myself, and have done a Fuzz Face and a Tonebender so far.  I notice that when I have it plugged into a live amp, and I connect the battery to the breadboard it makes a light thud, even with the circuit volume turned down.  Are you getting anything like that?

[bonzoboi]

@thermionix Yes, I do get a light thud when I connect the battery with the circuit plugged into a live amp.

[thermionix]

Somebody correct me if I'm wrong, but that indicates to me that your output cap and volume pot are working at least, maybe Q2 also.  I still think your Q1 voltages are off enough to maybe indicate a problem there, but I don't know what it might be.  My suggestion at this point would be to try a higher value Q1 collector resistor, maybe 56k to start with.  See if you get a sound, or at least see how the voltages change.

[bonzoboi]

@thermionix, Gotcha! I'll try that out. Also, I've been doing some more resistance testing with the multimeter today and here is where I'm getting large resistance read-outs:

- between Q1e and Q1b
- between Q1b and Q1c

Also, when I touch Q1c, Q2b, or Q2c with one of the multimeter leads there is a buzzing noise that comes out of the live amp.

Additionally, when I touch the right leg of the 8.2k resistor with a multimeter lead, and then touch the other multimeter lead to either the other leg of this resistor, or any other the legs on Q2, I get a reasonably loud thud and buzzing noise that comes from the live amp, as well as a beep from the multimeter. Any reasoning for these things? Or things I should replace/try out?

Hope this helps!

[bonzoboi]

@thermionix Did you mean to try a higher value Q2 resistor? I'm confused because there isn't a resistor on on Q1c, since Q1c goes to the Q2b. I tried a couple different resistors in place of the 8.2k resistor that connects to Q2c, but still didn't get anything. A big issue that I'm having is that no noise is coming out of the amp unless I put my hand on the output jack, so I feel like there's still a major grounding issue or something.

[thermionix]

I personally wouldn't be spending time reading resistances inside of a circuit.  Voltages are going to be more helpful.

Also, when I touch Q1c, Q2b, or Q2c with one of the multimeter leads there is a buzzing noise that comes out of the live amp.

But not Q1b, right?  I think your circuit is working from Q2b to output, and the problem lies at Q1.  It might just be biased into cutoff (no sound), rather than a bad or misconnected transistor.  Again I would try a higher value Q1c resistor.  47k, 56k, something like that, see what happens with the Q1c and Q1b voltages.

[thermionix]

@thermionix Did you mean to try a higher value Q2 resistor? I'm confused because there isn't a resistor on on Q1c, since Q1c goes to the Q2b. I tried a couple different resistors in place of the 8.2k resistor that connects to Q2c, but still didn't get anything. A big issue that I'm having is that no noise is coming out of the amp unless I put my hand on the output jack, so I feel like there's still a major grounding issue or something.

The 33k connects to Q1c and Q2b at the same point, that's the one I'm talking about.  Leave the 8.2k in for now.

[bonzoboi]

@thermionix Oh right the 33k, you're right! Forgot about that one. I'll try it out and get back to you quickly with some results! Thanks!

[bonzoboi]

So, with a 47k resistor in place of the 33k resistor, I got these voltage values on my transistors:

Q1e = 0.4 mV
Q1b = 2.39 V
Q1c = 2.986 V

Q2e = 0.64 V
Q2b = 2.986
Q2c = 3.61 V

I don't have any 56k transistors, and then next highest resistor value that I have is 100k.

[Electric Warrior]

I don't think this is leading anywhere. Q1's and Q2's collector voltages don't fit togther. With Q1C being so high, Q2C should be much lower. Rebiasing the circuit is not fixing this problem.

I bet something connects with Q1b or Q1c that shouldn't.

[thermionix]

I will defer to Dr. Warrior's expertise here.  Yeah the 47k didn't make much of a difference, but hey it cost nothing to try.  It might be time to pull everything off the breadboard, and check all the rows and rails for continuity and lack thereof, mabe there's a partial short from some debris inside the BB.  And check the value of each component while it's out of circuit, if you haven't already done so.  Short of that, maybe higher resolution pictures will help somebody here spot something.

[Ruptor]

Hi John

6. Positive ground to negative ground conversion?
No.

What does this question mean? If you are using NPN transistors instead of PNP then the ground must be negative.
Why don't you use the LTSpice simulator and put your transistors in it then you can see what the voltages should be around the circuit?
In fact I think I did a simulator circuit with your transistors already when I was playing around last week.
I just checked the voltages on the simulator using 2N3904 transistors with no input signal.
Q1 collector = 1.4V
Q2 collector = 3V
330R & 8k2 junction =8.8V

[thermionix]

The question is a standard one from the debugging instructions.  Assuming he answered "no" because he started with the negative ground NPN circuit and conversion therefore wasn't necessary.  But yes, back in the late 60s it was converted by Arbiter (?) from the PNP version.

[Ruptor]

Looking at the breadboard picture the right hand end of the 8K2 looks like it is connected to a Pot and a voltage rail via the vertical breadboard line. It should be connected to the 330R. Of course it might be I just can't see the bottom of the resistor wire.

[duck_arse]

ruptor - if you haven't already, can you post the circuit diagram you are working from, please, just so we can point at things accurately? also, what is the exact part number printed on the transistors you are using?

about your beeping meter - was it set to the ohms/continuity/diode test range when you were doing the blurt tests? if so, this is a bad thing. that/those ranges are for testing ONLY when the power is OFF, otherwise wrong readings will result.

from your Q1 voltages, the base is wrong, with grounded emitter it should be no more than 700mV-ish. your latest reading suggest this is still the case - so, perhaps - pull the input cap out of circuit, remeasure the Q1 voltages. has the base changed? if no, perhaps then pull the 100k from Q2 E to Q1 B, and connect it instead from Q1 B and Q1 C. this will rebias the first transistor to see if it will actually bias (I think). this all assumes you are using transistors with pinouts matching your layout, not BC's or L variants.