Mos-Face : weird occurences ?

Started by LucifersTrip, August 09, 2010, 01:45:41 AM

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LucifersTrip

I built a bunch of varieties fo the Fuzz Face with good results until I got to this one [Q1 = BC108b, Q2=2N7000]:
http://www.muzique.com/schem/fuzzface4.gif
http://www.muzique.com/schem/projects.htm [10th down]

I made sure I followed this specific instruction & triple-checked:
"The mosfet would be dropped in with its d-g-s leads going to the c-b-e pads respectively."

I got no sound whatsoever. Since I was successful with the other FF's right away, I thought it might be a loose
clip lead [I use clips for the pots & in/out jacks before soldering] so I jiggled the PCB around & made sure all connections were tight.

At one point I touched the top of Q1 [BC108b] and momentarily brushed against a spot where the + battery was connected.
I got a quick blast of fuzz!  

...so I took a clip lead and connected one side to the top casing of the BC108 and the other to the + side of the battery with a 8M pot
in series to simulate body resistance.   I got a great fuzz and both the attack & fuzz controls work perfectly...It works fine, as it should !

But I doubt I should make permanent a wire soldered from the casing of Q1 to the + battery [how would that be shown in a schematic?].

Anyway, I'll get some voltage readings now before and after that odd connection & check to see if the casing of Q1 is common to ECB or another point in the circuit.
One more note: If I lower the resistance of the 8M pot, the fuzz gates, and further the volume drops & the sound becomes clean.

Any ideas ?

thanx





always think outside the box

LucifersTrip

Update: Solved

I quickly discovered that C is common to the casing of the BC108.

So, in essence what I was doing was connecting the collector directly to + battery.

The only component between C and + is the 100K resistor. I checked it and it's blown !  Resistance = 1

...odd way to find my first dead resistor.


always think outside the box