Woolly Mammoth build issue

[coldbringer13]

I just finished up a Woolly Mammoth build (http://tagboardeffects.blogspot.com/2011/02/zvex-woolly-mammoth-vero.html).  I have triple check my layout, no solder bridges, and wiring is fine. 

The problem - when playing, the fuzz cuts in and out no matter if I strum hard or soft.   in addition, the pinch (when turned 100% on) creates weird "helicoptering." 

I am at a complete loss.  is this a component issue? 

Please help.

[EATyourGuitar]

check the pots? check the 3PDT?

[Elijah-Baley]

Post some pictures of the board and wiring.
Meanwhile, check all the ground contacts looking the schematic.

[Mark Hammer]

Check the value of the resistor in series with the Pinch pot. 

Depending on the transistors to some extent, increases in the total resistance of the path between Q2 emitter to Q1 base produce degrees of "choking" or "pinching" of the signal.  Most Fuzz-Face-based designs will use a single fixed resistor in that path, selected to assure that any variation in the individual transistors won't come too perilously close to sputteriness with that feedback resistor value.  The Woolly Mammoth, as a fuzz intended for bass and single notes, rather than chords, is designed to play with degrees of sputteriness as a tonal quality.  But make the resistance contributed by the fixed resistor and/or the pot a little too high, and you'll get something that doesn't sound good.

So, for the hell of it, first make sure that fixed resistor really IS 100k, and if so, try replacing the Pinch pot with just a piece of wire.  I'm not saying that will necessarily cure it, but at least you'll know that the problem lies elsewhere.

I made myself a Jen Fuzz II which is yet another FF-based design, as well as one of Jack Orman's MosFace fuzzes, and installed both a supply-current limiting "sag" switch, and a 3-position switch feedback-resistance switch.  When sag is increased and feedback resistance is high, it sounds simply awful; like busted Devi Ever pedal awful. 

[coldbringer13]

I will get pics, test the pots, & test the resistance between Q1 and Q2 wen I get home in a couple hours but i have a feeling it might be a resistance issue.  Thanks for the help!!!

[Gus]

That circuit is very sensitive to the betas of the transistors
http://www.diystompboxes.com/smfforum/index.php?topic=112217.msg1035665#msg1035665 is a thread with a screenshot to show how things change with transistor beta/hfe
The link you posted has voltages listed

I built a circuit fragment out of curiosity.
I needed to select the transistors to get the pinch to work over the full range

measure your transistors collector to ground voltages at minimum, middle and max settings of the pinch control
post them for more help.

Another thread that might help http://www.diystompboxes.com/smfforum/index.php?topic=114153.msg1059002#msg1059002

[PRR]

Others know this circuit's quirks better than me.

In general, "cuts in and out" is a bad connection. Could be jack or pot. But very often it is a solder joint that looks good, but isn't. The solder didn't actually "wet" both sides of the joint. There may be electrical contact by mechanical touch, but this cuts in and out.

[DekkerFuzz]

im having a problem with the wool control, i get hardly any fuzz until i get towards the end of the pots rotation with the pinch turned down, but loads of fuzz as soon as i start to bring in a bit of the pinch control, it sounds good but just doesnt react the way it should, i have used all the correct value pots and components and checked all traces, any ideas? any help greatly appreciated