Fuzz Face Clone Stopped Working - Any Help Appreciated

[williamsnrb]

Hi All,

This is my first post and I apologize if I am not thorough. I have a Fuzz Face clone that was built for me in a standard enclosure. It worked great for a few years, but then one day when I clicked the switch, it just muted the signal. I was told that the switch probably went bad, so I had it replaced, but to no avail. It has NOS germanium transistors, but I am not very educated on the build itself and do not know exactly how to test it with a multimeter. I know that this is not very helpful, but I was hoping that someone might be able to point me in the right direction with getting this thing fixed (either something I can do or maybe even send it to someone for repair). The only person I know to send it to was very expensive for labor - labor alone would be more than a new Fuzz Face.

The problem is that when the switch is engaged, the led lights up, but the signal is muted. When the switch is not engaged, signal passes through the pedal with no trouble or discernable change in sound. The switch has been replaced, so I wonder if a transistor blew. When the switch is engaged, if I tap the transistors with my finger, there is a short pop/static sound and it will start picking up radio stations through my amplifier. Any thoughts or guidance would be so appreciated.

Thank you!

[Marcos - Munky]

Welcome!

Post pics of your build. Also, with your multimeter on dc voltage scale, power the circuit, put the black probe on ground (any ground point will do it) and, with the red probe, check the voltages of each transistors pin and the voltage you're getting from your power supply. Those values should help us to know what's going on.

[williamsnrb]

Ok, I can do that! I'll reply back this evening with that information as soon as I am home from work. Thanks so much for the guidance. 

[williamsnrb]

Ok, sorry for the delay in posting. It was a late night at work. Here are some pictures of the pedal. I'll add the values that I get from the multimeter in a little while. I haven't been too successful with that so far.

[williamsnrb]

Ok, I have spent some time trying to figure out the multimeter readings and here's what I have found:

9.24v at the 9v jack.
9.24v at the 9v solder of the switch CPU board
9.24v at the 9v solder leaving the switch CPU board
9.24v entering the capacitor board
2.29v leaving the capacitor board
2.29v entering the transistor board
0.00v leaving the transistor board
0.00v at any point past the transistor board (pots)

One of the legs at the base of one transistor measures 0.01, but the other two legs and all legs on the other transistor read 0.00.

Does this mean the transistors need to be replaced? If so, is there anything else I should do other than take these two out and solder two new ones in? And should I be concerned about power polarity? Someone told me that I should be using a positive center power source and that I probably fried the transistors. But I used the same isolated standard power supply on this pedal for about a year with no issues before it stopped working. Any help would really be appreciated. Thank y'all!

[j_flanders]

I haven't seen this arrangement before but could that 'capacitor board' be some sort of 'buffered voltage supply'. Maybe someone can confirm.
If so, then 2,29V is really low to power those transistors and all the readings you'd get wouldn't resemble the values we're used to.
Is that (blue) 50k trimpot a bias pot or does it serve as a trimpot to simulate a dying battery, controlling the voltage supply?
Did you or the person that replaced the switch perhaps turn it? It does seem however that there's a black sharpie mark (kinda blurry) on the vero board, next to the trimpot marking the current position. Making it more likely to be a bias trimpot.

0V leaving the transistor board is normal. There's a DC blocking capacitor at the end of every circuit, just before the volume pot or output jack.

[Marcos - Munky]

I believe that "capacitor board" is in fact a negative voltage inverter. Indeed, it looks very similar to this one: http://tagboardeffects.blogspot.com/2012/05/negative-voltage-inverter.html

If you don't know/remember what that board is for, check the writings on the chip. But I'm almost sure it's a voltage inverter, and it's not working.

My first guess: it's a MAX1044, and you power supply it's not a regulated one. The MAX1044 can handle up to 10V, and your power supply may have oscillated and fried it. Well, kinda fried, since you're having a voltage output. But not a negative one, as expected.

And yes, you should be concerned about power polarity, or else you may fry your circuit. But that's not the case, since you used just the same power supply.

[williamsnrb]

Hey guys, thanks so much for the help! I'll bet you're right, Marcos - it does appear to be a negative voltage inverter. I did not make the pedal, so I don't know much about it. So you think that inverter board may be the problem and maybe the capacitors need to to be replaced? What if I took that board out and bypassed it and used a positive polarity power supply?

[williamsnrb]

I'm considering removing/bypassing the power inverter section and wiring the transistor board directly to the switch and using a positive center power cable to see if that works. Is that a good idea? I just don't know what to do from here.

[Marcos - Munky]

The best idea would be to fix the inverter board. It's probably a dead ic, so it's just a matter of removing it and putting a new one in the place. It may died because a voltage input of more than 10V or, since the board isn't fixed to anything and doesn't have any insulation on the copper side, it may have touched the enclosure and shorted something.

First, let's check if the fuzz is working. Try to use a battery. For some reason, postimages isn't working for me today, so I can't open the pics to say which wire goes to which pole of the battery, but I can describe how to wire it correctly.

The voltage inverter board have two "power output" wires. One is connected to ground (probably the black wire) and the other is connected to the pin 5 (probably the red wire). Connect the ground wire to the positive side of the battery and the other wire to the negative side of the battery, and check if the circuit is working.

[williamsnrb]

Ok, so just to make sure I connect the red wire to the negative pole of a 9v and the black wire to the positive pole?

[williamsnrb]

So I ran the 9v as instructed to the positive and negative lines going into the transistor board and got signal to pass through to the amp and the pots changed the volume, but no fuzz came through.

[Marcos - Munky]

So the transistors are still good. Nice!

Does the gain pot do anything to the sound?

[williamsnrb]

The sound did change some with adjustment of all the pots with the volume making the most difference. I resoldered the wires back and interestingly I am now getting 2.28v at the base of once transistor, but still 0v at the base of the other. And once I resoldered it, the switch is now muting all signal again.

[Marcos - Munky]

It isn't working again because the voltage inverter is not working. So, resoldering the wires back will take it back to the initial non working state.

Return to the battery setup, put the multimeter on voltage mode, put the black on ground and, with the red probe, get voltages of each transistors' pin. Also, can you contact the person who built it and ask which layout they used?

[williamsnrb]

Ok, I pulled the wires and went back to the battery setup. It's weird. When the positive probe contacts the legs of the transistors, the transistors both start out at 6.6v and start going down quickly to 0v. Hmmm... before, I wasn't getting a voltage at all at the base of one transistor. Now, they both read 6.6v and start dropping. Now I'm wondering if I should just bypass the power inverter and plug the black and red wires from the switch directly to the transistor board. I could just use a red cord from my power supply for positive center.  Is that a good idea or no?

[williamsnrb]

Nevermind about the red plug. I was confusing center positive with positive ground. I think I will bypass the inverter and plug up to my isolated power supply and see what happens. I'll post the results shortly.

[williamsnrb]

I wired it up by bypassing the inverter and actually am getting some quiet static from the pedal and it varies when the knobs are turned. No guitar signal, but at least it's not muted. I think I need to replace the transistors. I'm going to try that (I need to order them first). If that doesn't work, I might be at the end of my journey with this pedal. Haha I'll keep this updated with what I find out. Thanks!

[Marcos - Munky]

How exactly did you bypassed the inverter? You may have shorted your power supply, that's one reason for it to stop working.

Also, don't take me the wrong way, but please stop to do random things with your pedal. You may end up damaging it by doing this. You don't need to replace the transistors, we know they're good because you got the circuit to work with the battery. Indeed, we already know you have a dead ic on the inverter board and tracked down the problem to the gain part of the circuit.

As I've asked, return to the battery setup, post the voltages on each transistor pin and ask the builder which layout did he used. It's a simple circuit, simple enought to trace it from the board, but it's easier if we have the layout they used.

[williamsnrb]

I hear you. I am trying to figure it out without bothering everyone too much, but I am not sure what is going on. By "bypassing the inverter", I mean I just ran the positive and negative wires leaving the switch to the input of the transistor board. I don't have the original schematic. I did not build the pedal, so I'm just trying to figure it out along the way. I was hoping that if I bypassed the inverter and everything else was fine, that it would work fine. I've verified that the power supply output is functioning and is isolated.