Is this ever going to work? Fuzzface problems revisited

[saxtim]

I decided to start a new thread instead of people wading through the 4+ pages of my last thread about my fuzz face.  I pulled everything off it, confirmed parts and placement, put it back together and I'm back to square 1.

I'm building a PNP Negative Ground version and my voltages all look OK:

(using small bear trans.)
Q1 E8.95 B8.80 C8.21
Q2 E8.37 B8.21 C4.75

(collector measured an even 4.5 yesterday, but today it's a bit cooler - that may have made the difference.)

However the unit doesn't perform correctly:

Sustain notes/chords are a problem as the effect seems to stutter and cut in and out as the notes decay (ie when it gets to a certain level of softness the distortion sorta flicks on and off before finally leaving only a clean signal).

Playing softly produces a non distorted signal.

I have no sustain at all in the high notes. You play a high note and the distortion flips on for half a second or so and then flips off - it sounds like you're playing staccato - no sustain at all.

I've tried plugging in some 2n5087's in place of the trans from small bear - no difference to the problems

I'm curious about the orientation of C1 (elec. on the input) - at the schematic at GGG it's shown with the neg. side facing the input.  It's shown the same way as the positive ground version, and the original schematic at RG site also has it orientated this way.  The smallbear bear face (which I'm assuming is negative ground?) has it orientated the opposite way.  I measured the neg/pos side with my DMM and as it is, the negative side is facing the most negative reading, so I guess it's ok, I'm just not sure.  I'm starting to clutch at straws now anyway - I have no idea what's going on.

Tim

[Steve C]

I'm building a PNP Negative Ground version and my voltages all look OK:

(using small bear trans.)

Q1
E8.95
B8.80
C8.21

Q2
E8.37
B8.21
C4.75

Since you're are building a PNP Fuzz Face your power supply needs to be the (-) negative side of the battery, and the (+) positive side of the battery is your ground.  This is the opposite from most pedals.

You should measure zero (0) volts at the emitter of Q1 regardless of which version you are making.  So make sure the point where you connect power above the 33K resister to the collector of Q1, is to the negative side of the battery, and that all points that connect to ground are connected to the positive side of the battery.

PNP Fuzz Face has POSITIVE ground NOT negative.

[saxtim]

You should measure zero (0) volts at the emitter of Q1 regardless of which version you are making. So make sure the point where you connect power above the 33K resister to the collector of Q1, is to the negative side of the battery, and that all points that connect to ground are connected to the positive side of the battery.

PNP Fuzz Face has POSITIVE ground NOT negative.

Check this schematic - http://www.generalguitargadgets.com/v2/diagrams/fuzzface_sc_pn.gif

This is what I'm building off.  I don't really understand the process that well, but I understand that the PNP postivie ground circuit can be converted to a Negative ground circuit.  At least that's what JD's got happening (I think he's done it with several other projects as well.)

As you can see in this schematic Q1's emitter connects to +9V, hence my +8.95 volt reading.

This is correct, no?

tim

[Chris R]

i'd stick with + ground.. i just finished switching mine over from -...

see the other thread for details:  http://www.diystompboxes.com/sboxforum/viewtopic.php?t=16846

[petemoore]

emitter [Q1] IS ground on this ckt...
 to measure any voltage you have to have current.
 If both leads of a DMM are touched together [like Q1 and emitter to ground need to be in a FF] you will read 0.0000 volts ie there should be absolutery No Current or voltage between Ground at Ground, Ground at Q1 Emitter, or anywhere else that is connected to Ground.
 If If Q1 IS connected to Ground there Will Not Be Any voltage if you test between Q1 emitter to ground, which is also AT ground And also IS ground in fact anytime you try to get positive AND negative from one source like Ground You wont be able to find any voltage from Ground to Ground...
 try getting a set of test clips and conect each one to either end of the same wire, then test with the voltmeter for continuity between the clips.
 then, clip one of the clips carefully to only the Emitter of Q1, clip the other clip to 'ground'
 Then test the voltage between Emitter [at] and ground.

[petemoore]

I went on a bit long about that ground problem but I think it is bound to help...getting that emitter grounded.
 Sometimes I just use whatever transistors I have around if they're the right PNP for PNP ckt etc.
 Usually even if they're not matched well I can get a squelch noise from them that sound amplified [ie they're turning on].

[Steve C]

Check this schematic - http://www.generalguitargadgets.com/v2/diagrams/fuzzface_sc_pn.gif

I don't really understand the process that well

As you can see in this schematic Q1's emitter connects to +9V, hence my +8.95 volt reading.

This is correct, no?

tim

Okay, you should have posted this with your original voltage readings.  I see why he's doing that.  

I'd still treat the positive as ground when measuring voltages.  So put your negative lead on the positive and take your readings with the positive lead then post those readings.  These readings will make more sense to everyone.

[saxtim]

petemoore - I didn't get what you were getting at (with regards to ground), but after reading Steve C's last post I'm finally on the same page as you.  

I'd still treat the positive as ground when measuring voltages. So put your negative lead on the positive and take your readings with the positive lead then post those readings. These readings will make more sense to everyone.

I was taking my voltage measurements from the point on the schematic that are shown as being grounded - ie 0 volts, however I should've been using the +9v as my ground reference.  So I guess what was mucking me up was I was thinking of the +9v as +9 above ground and not being 'ground'.  Still, the net result is that my readings just had to be minus from 8.95 (my supply voltage) to get them referenced to the positive, rather than 0 volts.  

Anyways, I remeasured the correct way to make sure:

Q1
E 0 B .15 C .72

Q2
E .56 B .73 C 4.40

These to me still look right - emitter more negative than the base in both instances.  I have close to 4.5 Q2's on the collector (and if you read my earlier thread I'd experimented with the collector resistor through a whole range of voltages, from well below to well above 4.5 - I couldn't find one that made the effect work correctly.

I replaced the 1kb fuzz pot for fear it may have been malfunctioning - made no difference.

What now?

Thanks,

tim

[petemoore]

between base and emitter you should be seeing at least .7v difference for the transistor to turn on.
 Ckt ground is always where all those ground [increasingly shorter horizontally stacked lines] marks connect...that's where the one lead of the DMM should stay while the other checks the voltage differences from there. I think you got that...PNP and/or NPN...stick your one DMM lead to where ground is on the ckt. [Q1 emitter, 1kpot goes there, volume control goes there [make sure they do all make ground using the beep function] ...then set the meter to DC Volts, put yer one lead to ground and measure voltage at different points in the ckt with the other DMM lead.
 I'ts very easy to miss a resistor color code, I don't know how many times you've checked this but I've missed them repeatedly and then discovered it...
  I still think this one can get going...but time is to be considered too...at some point I start over...not to say you should choose to do this.
  When building, I use the DMM to verify the resistance of a R is actuall very close to what is specified in the schematic...one little color code line differecne is easier to find this way...I have a small bin of resistors pulled off the reel [to be used for a specific R value in a ckt] that were tested and found as the wrong value by the DMM...
  The more I use the DMM during building the less I have to Debugg it seems...I like to check everything I can think of useing the Beep, resistance, and Voltage modes of the DMM...
  Checking in ckt resistors is not recommended because the current may find another way [besides throught the resistor] from one DMM lead to the other by flowing around the resistor through the ckt....but...I Have found missed R values in ckt:
  test a resistor in the ckt. onlu heed the DMM's stated value if the resistance is greater than specified for that part...if it's less than that R value, there is a great liklihood that current is flowing around and through that resistor [in ckt].
 Wiring error is  and very deceptive and hard to track down...
 I appreciate the efforts and patience you're providing for this Ckt.
 I sincerely think and hope that soon this problem will give you a little chuckle, and you'll be trying another FF type ckt soon...I musta done 10+ FF types...they can be tricky little buggars...You've put your time in...to be sure...[FF's do not recognize efforts, only when everything's just right do they respond]...keep at it, I think soon you'll find the rewards are worth the time and frustration...You are learning more than you realize with all this [some consolation at this point huh?]
 You'll get it though...it Has to Work when it's allright !!!
 These things Always follow a strict regimen of law...

[javacody]

Pete, that checking the value of your components as you go idea is actually a pretty darn good one. If you print out your schem, you could double check the part on your dmm, solder it in, and cross it out.

[saxtim]

Ckt ground is always where all those ground [increasingly shorter horizontally stacked lines] marks connect...

I'm familiar with the ground symbol, and how to use a DMM - I'm not really super experienced, but I have successfully debugged several circuits.  This however is my first PNP circuit and the postive/negative thing - That's what was screwing me up.  Please check the schematic at:
http://www.generalguitargadgets.com/v2/diagrams/fuzzface_sc_pn.gif

You can see here (schematic) that Q1's emmiter is NOT shown to be grounded, but connected to +9V, however in the positive ground PNP circuit schematic (same site) it is shown grounded.  As I said, I think the confusion had come from me measuring from the indicated ground points in the above schematic, rather than using the +9V as a ground reference.

Anyways, that doesn't really matter any more, I've got some voltage readings now that people can make sense of.

When building, I use the DMM to verify the resistance of a R is actuall very close to what is specified in the schematic...one little color code line differecne is easier to find this way...I have a small bin of resistors pulled off the reel [to be used for a specific R value in a ckt] that were tested and found as the wrong value by the DMM...

I've done this.  I've infact done it 3 times - Firstly I gathered all components, check for values (with DMM), labelled them, and put them in a little plastic bag.  I did this for several effects at once, one bag per effect.  When I came back to a few days latter to build the fuzz face, I had everything I need bagged up.  I pulled all the stuff out of the bag, re checked vales with DMM before placing in the circuit to make sure I'd done it right.  The third time I checked was when I pulled the whole thing apart and re-rechecked all component values with the DMM - definate about all component values and polarity on the the caps.  

between base and emitter you should be seeing at least .7v difference for the transistor to turn on

I'm building a germanium PNP circuit (negative ground) - my understanding is that the difference between base and emitter ("0.0 to 0.3 for germanium") will be not as big as you'd see in an silicon circuit (and the emitter is more neg than the base, where as NPN is vice versa).
quote is from the www.geofex.com debugging page.

From this the differences between my base/emitters in both cases look fine, also consider the voltages posted at GGG - they show only .1 V between the base and emitter in both transistors:
http://www.generalguitargadgets.com/v2/index.php?option=html&file=instructions/fuzzface_inst.htm&Itemid=51&op=page&SubMenu=

Indeed, my voltages are quite similiar (within .2 volts all the way)

So what now?

I'm at a complete dead end, I'm starting to think this thing really will never work!

tim

[saxtim]

Ckt ground is always where all those ground [increasingly shorter horizontally stacked lines] marks connect...

I'm familiar with the ground symbol, and how to use a DMM - I'm not really super experienced, but I have successfully debugged several circuits.  This however is my first PNP circuit and the postive/negative thing - That's what was screwing me up.  Please check the schematic at:
http://www.generalguitargadgets.com/v2/diagrams/fuzzface_sc_pn.gif

You can see here (schematic) that Q1's emmiter is NOT shown to be grounded, but connected to +9V, however in the positive ground PNP circuit schematic (same site) it is shown grounded.  As I said, I think the confusion had come from me measuring from the indicated ground points in the above schematic, rather than using the +9V as a ground reference.

Anyways, that doesn't really matter any more, I've got some voltage readings now that people can make sense of.

When building, I use the DMM to verify the resistance of a R is actuall very close to what is specified in the schematic...one little color code line differecne is easier to find this way...I have a small bin of resistors pulled off the reel [to be used for a specific R value in a ckt] that were tested and found as the wrong value by the DMM...

I've done this.  I've infact done it 3 times - Firstly I gathered all components, check for values (with DMM), labelled them, and put them in a little plastic bag.  I did this for several effects at once, one bag per effect.  When I came back to a few days latter to build the fuzz face, I had everything I need bagged up.  I pulled all the stuff out of the bag, re checked vales with DMM before placing in the circuit to make sure I'd done it right.  The third time I checked was when I pulled the whole thing apart and re-rechecked all component values with the DMM - definate about all component values and polarity on the the caps.  

between base and emitter you should be seeing at least .7v difference for the transistor to turn on

I'm building a germanium PNP circuit (negative ground) - my understanding is that the difference between base and emitter ("0.0 to 0.3 for germanium") will be not as big as you'd see in an silicon circuit (and the emitter is more neg than the base, where as NPN is vice versa).
quote is from the www.geofex.com debugging page.

From this the differences between my base/emitters in both cases look fine, also consider the voltages posted at GGG - they show only .1 V between the base and emitter in both transistors:
http://www.generalguitargadgets.com/v2/index.php?option=html&file=instructions/fuzzface_inst.htm&Itemid=51&op=page&SubMenu=

Indeed, my voltages are quite similiar (within .2 volts all the way)

So what now?

I'm at a complete dead end, I'm starting to think this thing really will never work!

tim

[Chris R]

try the + ground schem.

i had a hard time bias-ing and other noise problems with the - ground.. but as soon as i switched it over.. it worked like a charm.

C

[saxtim]

try the + ground schem.

I'm considering this, but I'm reluctant to - mainly because the PCB I designed isn't like the one at GGG which can be switch between positive/negative by adding and removing a jumper and swapping battery terminals

tim

[rx5]

saxtim,

For me, Ive tried wiring my PNP postive ground fuzz to a negative ground BUT I DID encounter problems... I hear LOW freq oscialtion when FUZZ is set to max.....

if your having problems with your neg ground Fuzz, just wire it to postive ground ....

[bwanasonic]

very strange posting problems on this one...

[bwanasonic]

Well first off- I think we will all celebrate when you finally get a working Fuzz Face! My first attempt at a FF circuit was also PNP neg. ground and I could not get it to work properly. I was not commited to a PCB layout ( used pad-per-hole perf) so I started from scratch with the pos. ground version, which works marvelously. For all the time you've invested in this project, you may just want to wire up a piece of perf with a PNP/ pos. ground version. Or etch a new board with this config. It really does sound better with a carbon battery and the battery life is almost comicallly long, so an adapter free version is not a big problem.  

Good luck
Kerry M

[bwanasonic]

As Strong Bad would say: "Holy Crap!"

[petemoore]

I just looked at the schem and it's much different than I'd expected, also I don't understand it.
 I think there's a way to make this ckt work, but I just don't get it.
 I'm gonna look again...after looking again I'm decideing that going [if you have PNP's] with a regular pos ground version would make it easier for me to understand and figure out...if you're using film caps for everything except the 22uf, the 22 uf and the battery wires would only need to be changed?
 I put a question mark there, partly because you're study, references, and dialogue were well thought out and written !
 Start [if you have them] with garden variety PNP si's mayby for initial testing and taking readings...I always check stuff like from battery clip + to- on beep mode, all the grounds are made, pos is getting to where it should ..before powerups.
 I'm a little surprized [like me, I don't think they registered which FF version] that someone who's tried this...maybe now someone will see the ckt and make better heads or tails of it...if that doesn't happen soon I would go with the 'reg' pos ground FF schematic....or soemhow word a new topic asking about how this ckt 'goes'...I just don't see how...
 Try to form a specific question about the function of the ckt ...how does that work
 Easiest thing at this point I think maybe is make those little PS changes to make it like a 'regular' FF...

[bwanasonic]

Was really just trying for the first quintuple post....