Moen - Fuzz Moo  [schematic]

All about modern commercial stompbox circuits from Electro Harmonix over MXR, Boss and Ibanez into the nineties.
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bopster
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Post by bopster »

I've followed the veroboard layout exactly, getting signal through it when I've connected everything up with clipleads, but no fuzz. maybe a very slightly driven signal, but even that may be wishful hearing. I've put sockets in all the transistor spots, but even running MPSA13's (I got desperate) in them, no fuzz. Is this me being a total noob, or is something not quite right? Any help would be greatly appreciated.

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modman
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Post by modman »

bopster wrote:I've followed the veroboard layout exactly,
How come you're so sure? You think you followed it exactly... That don't mean nothing.
bopster wrote:getting signal through it when I've connected everything up with clipleads, but no fuzz. maybe a very slightly driven signal, but even that may be wishful hearing.
At least this is something: signal is coming through, but no amplification. Check: battery, pots (turned down? or soldered wrong etc)
bopster wrote:I've put sockets in all the transistor spots, but even running MPSA13's (I got desperate) in them, no fuzz.
https://www.fairchildsemi.com/datasheets/MP/MPSA13.pdf
It says Darlington transistor. If you, like me don't have a clue what that means just search the forum for combination of "mpsa+darlington". I found this interesting post:
Subject: Question regarding running very high HFE transistors(gating)
Mr.Grumpy wrote:The MPSA is a darlington, basically two transistors "ganged" together for more gain. Biasing would be different for a darlington vs. a standard transistor. You don't need the ridiculous amount of gain provided by a darlington, especially in that first stage. The first stage is an input buffer, and shouldn't clip. The distortion happens on Q2 and Q3. The Q4 is also a buffer to drive the 'lossy' tone control.
Just put another 2N2222 in Q1 and I predict your fuzz will behave much better. They have them at Radio Shack. :secret:
Mr.Grumpy wrote:
nightendday wrote:perhaps a stupid question, but could I just feed the transistor more power and bias it correctly? thus hitting the front of the fuzz with stronger signal?
That first stage is already wired as "voltage divider" biasing scheme, which is supposed to compensate for variations in transistor gain. But not for this circuit, apparently. I don't think a small darlington transistor is even intended to work as a linear amplifier, with the insanely high gains they have, they are really only useful as an on/off switch - they are either in saturation or cut-off mode.
Sorry to be a wet blanket, but the circuit will be much more controllable if it's built according to the schematic - meaning a regular bipolar NPN transistor for Q1. You can try different types and see how you like it, it won't hurt anything. 2N2222, 2N3904, and 2N5088 will all work in the circuit.
bopster wrote:Is this me being a total noob, or is something not quite right? Any help would be greatly appreciated.
A total noob would be scared that if he puts in the wrong transistor, the house will explode. He would also start off with a simple circuit....
Read the thread from the start, know that you are building a Big Muff...

Check your parts box for any plain jane NPN Amplifier transistor, check the pinout (Emitter Base Collector)
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Post by bopster »

Thanks for your reply. I already tried all the ones I had, 2N5088, 5089, 3904, etc. MPSA13 was the last one I tried. Battery is good, and pots were taken through the entire range. They had an effect on sound, but nothing that made it fuzzier. Some volume control and tone variation (depending on which pot was adjusted).

Yes, I cannot be absolutely positive that I've done it exactly like the layout pictured, obviously I don't have the experience under my belt yet, but I have checked and checked again, and it would seem like all my components are in the same spot as the picture.

Stumped :scratch:

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Post by modman »

bopster wrote:I already tried all the ones I had, 2N5088, 5089, 3904, etc. MPSA13 was the last one I tried. Battery is good,
That's not what you said the first time... Please measure the voltages on your transistor (one lead to ground, another on different transistor pins) after you put back the 2N5088 that was specified. Post your voltages, or better, compare to this page:
bopster wrote:pots were taken through the entire range. They had an effect on sound, but nothing that made it fuzzier. Some volume control and tone variation (depending on which pot was adjusted).
Do you have a switch conncected? Is the bypass volume equal to the volume when engaged? And tone control and volume do work?
I don't have the experience under my belt yet, but I have checked and checked again, and it would seem like all my components are in the same spot as the picture.
I am sure they are, but check for shorts: are the connection conducting properly? is the signal path connected to the ground path through some gone astray solder. Don't know how, ask Katie:


As it's just a Big Muff, you can you transistor voltages against this: http://www.generalguitargadgets.com/pdf ... struct.pdf
Component Location Voltage
9 volt power supply 8.8
Q1 Collector 3.9; Base 0.6; Emitter 0.03
Q2 Collector 3.8; Base 0.6; Emitter 0.03
Q3 Collector 3.8; Base 0.6; Emitter 0.03
Q4 Collector 4.0; Base 2.5; Emitter 1.8
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Post by bopster »

Power supply 9.4v

Q1 0.0 0.0 0.0
Q2 4.0 0.64 0.02
Q3 4.08 0.64 0.02
Q4 3.93 1.67 1.15

Obviously an issue with Q1. Presumably this is caused by poor soldering or something? Transistor tested ok by itself, outside of the circuit. Swapped it out anyway. Same result.

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Post by howmuch »

Has anyone opened up the newer, smaller Moen Fuzz Moo?
Moen Fuzz Moo enclosure Small - HTB1jiUKX5YrK1Rjy0Fdq6ACvVXa8.png
Moen Fuzz Moo enclosure Small - HTB1jiUKX5YrK1Rjy0Fdq6ACvVXa8.png (141.11 KiB) Viewed 1036 times

I'm wondering if it's still transistor based, or whether it's an op amp big muff.
There's a DIY kit on aliexpress that has an enclosure a lot like that Moen and the PCB is for an op amp muff.
Landtone Fuzz kit - H115310e2307f4c0f971526470ffe6446k.png
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Post by TaperChuck »

Reviving this thread...

I bought the new smaller version hoping to use it to tinker with some modifications...
But, it's surface mount. :(

The pedal is a little noisy.
There's enough room to remove some surface mount resistors and replace them with through hole parts.

Is there any easy way to make it less noisy? Would replacing the 100r emitter resistors with 150r's as mentioned by earlier in the thread? I can't draw up circuits, but I can follow directions. There's enough room in there to replace the three SM resistors with through holes if it would help.
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MoenFuzzMooSMGuts.jpg

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CheapPedalCollector
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Post by CheapPedalCollector »

2n5089's would probably help a bit and yeah the 150s or even 220s would help a little bit. It's a multistage high gain circuit, so it's just par for the course really.

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