transistor voltages on a fuzz face

[cove]

i finished the fuzz face from general guitar gadgets and checked the transistor voltages and got the following

Q1
c- 8.5 volts
b- 8.5 volts
e-.23 volts

Q2
c, b, e - 8.9 volts

any ideas...transistors bad...short ?....thanks

[Peter Snowberg]

From a glance it looks like you have bad ground connection around the "fuzz" pot. Check your connections going to the emitter of Q2 and I'll think you'll find the problem.

Good luck! (no luck needed really, it's all repetition and observation... you'll get it!)

Take care,
-Peter

[petemoore]

Ok then, pull the transistors, set the DMM to beep, check between Q1 E/B, and B/C...same for Q2 the only two pins that should be connected are Q1C and Q2B...looks like there could be a short between the transistors pins...the DMM will tell.
 looks like the 'same/same' reads on the pins are connected and they shouldn't be ..ie ...Q2's pins, and c/b of Q1
 What circuit are you building neg ground?

[cove]

these are the latest voltages checked and rechecked.
Q1 voltages are as follows

collector .1v
base 8.9 v
emitter 9.1 v

Q2

collector .1 v
base .1 v
emitter 9.1v

battery 9.5 v
heres the link to the project
http://www.generalguitargadgets.com/v2/diagrams/fuzzface_lo_pn3.gif

Q1 e should be 9.0 volts and Q1 c is the same as Q2 b which they are. and according to the circuit if iam reading it right base of Q1 and emitter of Q2 should match.
does that look right?

so maybe things are okay?

are there adjustments with turning down the guitar volume  as to not overdrive the box?
thanks

[cove]

these are the latest voltages checked and rechecked.
Q1 voltages are as follows

collector .1v
base 8.9 v
emitter 9.1 v

Q2

collector .1 v
base .1 v
emitter 9.1v

battery 9.5 v
heres the link to the project
http://www.generalguitargadgets.com/v2/diagrams/fuzzface_lo_pn3.gif

Q1 e should be 9.0 volts and Q1 c is the same as Q2 b which they are. and according to the circuit if iam reading it right base of Q1 and emitter of Q2 should match.
does that look right?

so maybe things are okay?

are there adjustments with turning down the guitar volume  as to not overdrive the box?
thanks

[cove]

checked everything again and got

Q1
e-9.1v which is right to the v+
b-9.04 v
c- 8.65v

Q2
e 8.65v
b-8.55v
c-2.2v

does this sound okay

[petemoore]

where does the red wire from your battery clip go?
 Is this neg ground?
 Emitter goes to V+  ?
 Take a look at the debugging page, lots of good stuff in there.
 A link to the schematic [or name of] would make it easy to see what you're trying to do.
 Also what kind of transistors are you using?

[brett]

Assuming this is a germanium transistor neg earth build, there's a problem on Q1 (at least).  The collector should be about 1.1V less than the emitter (which is at battery voltage).  i.e about 8V.  Also, the base should be about 0.3V lower than the emitter.  Otherwise the transistor will not be switched "on".

Similarly, the base and emitter of Q2 look too close together (voltage-wise).  And it is best (tho not completely essential) if the collector of Q2 sits around the 4 to 5 volts level.

Are you using a 33k resistor on the collector of Q1 and somewhere around 5 to 10k on the collector of Q2

Perhaps you should think about building one of RG Keen's transistor testers (geofex.com).  That will identify any problems with the transistors.

cheers

[cove]

sorry for any confusion there were no negative values here are the correct ones
Q1
e 9.1v which is right to the v+
b 9.04 v
c  8.65v

Q2
e 8.65v
b 8.55v
c 2.2v

iam using this project
http://www.generalguitargadgets.com/v2/diagrams/fuzzface_lo_pn3.gif
and its negative ground
the project seems to work but might be to dirty sounding, i just need to know do i have
to still correct something or am i okay .

yes to the 33k resistor on Q1
no using a 3.9k resistor on c on Q2 that was the resistor value that was given with the matchng pnp transistors


thx

[petemoore]

It is marked as a NEG Ground circuit.
 It looks to me that Battery + is going to ground...ie POS ground...
 Is there a plain schematic of this thing?
 The last two times the fix for this is....Scrap that diagram, pick out a FF with POS ground...should be much much easier from there.
 We tried a few times with that diagram, I never understood the reason for it or why it won't work.
 If it were mine, I'd get rid of the DC jack, hook batt pos to ground and neg to the 'top' Use PNP transistors with the emitters toward ground.
 Unless you're a Wiz with super filtered PS, you'll find the FF doesn't like the Wall Warts...also the internal resistance of the battery is part of the FF circuit.
 So there's your problem...that diagram gets 'em [you] once in a while...
 IIRC the Newest FF's from Dunlop use this wierd PNP Neg gnd.
PS hookup..Maybe someone can figurewhat it takes to make that diagram work..as it is it serves as a trap for wary FF builders.
 So Pos supply  to ground, the bypass caps pos to ground also [22uf], I would just say use film caps for input and output. then the PNP Q's with emitters toward Gnd.
 Just look for a schematic that says PNP POS Ground, only a few changes will need to be made.

[cove]

thanks so much for your help on the forums...attached is link to the pos grnd FF . can i change the neg grnd to pos ground and leave out the dc power jack and make this work.
any suggestions you have to still use the pcb and parts to make it work would be helpful

pos grn : http://www.generalguitargadgets.com/v2/diagrams/fuzzface_lo_pp2.gif
neg grn: http://www.generalguitargadgets.com/v2/diagrams/fuzzface_lo_pn3.gif

thanks again
bruce