FUZZ FACE Yaff debugging please...

[LucifersTrip]

I recently built 5 different fuzz & sound effects circuits and got em all working on the first shot but this simple one has started me on a bad streak. I'm still a novice, especially at debugging since this is my first of 3 duds in a row.

This is the Yaff variation on the Fuzz Face. Since the original uses a PNP transistor and this uses NPN, all the polarities are reversed (caps and +/- battery) from the original Fuzz Face.


I get no sound at all.

Schematic:
http://www.muzique.com/lab/yaff.gif

I made 2 changes since I didn't have the exact caps. I used a 2uF instead of the 2.2uF and a 20uF instead of the 22uF

I'm using a slightly used battery, 9.4v.

The 2 transistors are 2N2369, NPN
Datasheet:
http://www.datasheetcatalog.org/datasheets/50/490431_DS.pdf

The voltages:

red battery lead = 7.4
black battery lead = - 1.66

Q1
C = .85
B = .22
E = 0

Q2
C= .24
B= .85
E= .24

pretty low?

On a side note,
If I disconnect the fuzz control (the one side of the 1k pot from where R4 & R8 meet), I do get a sound...just a clean tone like a bypass.

Those voltages are:

red battery lead = 8.66
black battery lead = - .5

Q1
C = 6.6
B = .5
E = 0

Q2
C= 6.1
B= 6.6
E= 6.1

Any help would be great. I didn't think much could go wrong with this simple one, except for a bad part...

thanx

[petemoore]

Q1
C = 6.6
B = .5
E = 0

Q2
C= 6.1
B= 6.6
E= 6.1  Check the resistance of the points where you find this voltage, this pin should be nearish ground, 0v.

[R.G.]

Q2
C= .24
B= .85
E= .24

When the collector voltage equals the emitter voltage, generally the transistor is either shorted or saturated. In either case, no signal will go through.

Remove power, check for collector shorted to emitter with your ohmmeter. If there is no short, check for whether the collector actually goes through the collector resistors to power. If the collector resistor is open, the collector is always saturated.

If I disconnect the fuzz control (the one side of the 1k pot from where R4 & R8 meet), I do get a sound...just a clean tone like a bypass.

The circuit cannot work properly if the fuzz control is disconnected. It's part of the DC biasing setup.

[LucifersTrip]

I built the circuit on a pcb minus the input/output jacks and pots, which I used clip leads for. I didn't want to finalize anything until I had it working.

I had a loose clip lead to one of the output jacks and got the wrong voltages. Even with the clip lead tight, still no sound.

But here are the correct voltages:

Q1
C = 1.07
B = .32
E = 0

Q2
C= 7.94
B= 1.07
E= .49

Is a  possible problem B on Q1? According to the debugging FAQ, "the base must be more positive than the emitter by about 0.4 to 0.7V for silicon"

thanx again