first time fuzz build .. debugging help??

[saint44]

this is my first pedal build, i have modded a few, ... i used the pcb and layout from \P Bryant for \jen fuzz III,  no sound, bypass works fine.  the following are the voltages through various components with negative on DC input.  i have substituted 2N5088 instead of the BC 239C (dont have any).

+ve to board - 8.90V
input trans - E 6.84, B 4.14, C 8.98
middle trans - E 1.29, B 0.00, C 1.49
output trans - E 1.49, B 1.49, C2.18
after 1M resistor 4.14
after 6K resistor 6.9
after 150K resistor 1.29

unfortunately i dont know how to post a few pics or links to layout of the build.

[LucifersTrip]

it looks like a bad/wrong  joint/component problem...

Q2E is grounded, should be 0

For Q1 to Q3, the E voltage should be less than B should be less than C

Did you mix up measuring E and B or reverse the pinouts?

since Q2 is hooked directly into Q3 and Q2E is not 0 like it should be, start looking for errors around Q2.

I'll dig up the voltages from my Jen




edit:
from my Jen Fuzz
http://fuzzcentral.ssguitar.com/schematics/jenfuzzschem.gif

EBC
Q1 > 5.96, 6.12, 9.04
Q2 > 0, .58, 1.28
Q3 > .67, 1.28, 4.71

[saint44]

thnx,thats the one i used, according to pcb and layout diagram from same all Q's are CBE from top to bottom.  i am such a newbie, i used my multimeter transistor slot and had the highest values for HFe having EBC pins (left to right flat side facing).  i tried several transistors, is there a reason why there is no voltage through the 1N914 diodes?  i have pics of my project jsut dont know how to post them.  thnx for help.  i'll start testing around Q2, i also tested the 4k7 resistor going to B of Q2 and cold not get a voltage reading, but the resistor value was right??  is that wierd?

[GibsonGM]

The cap before the 4k7 resistor stops DC from being able to go from Q1 to Q2...only AC can pass thru - capacitors block DC voltage -, and it you're not playing at the time, no reading!  Cool eh?

The diodes are the same way.  There is a capacitor after the collector of Q3, so no DC voltage can flow out to them. Therefore, there is no conduction.   BUT - when you play, your AC input (the guitar signal) is amplified and then passes thru that cap, hits the diodes, and gets clipped = fuzz.    A typical silicon diode like that needs .5v or greater to 'turn on'.    AC voltage, in this case.   It's all about how we change the AC coming from the guitar by using DC INSIDE the circuit, then 'taking the DC away' and having a modified AC signal at the output!

Keep trying, you'll figure out what's wrong )  Luc's. Trip is pointing you well.  Check this data sheet to be SURE you got the pinout correct!  Look at the pic on page 1:  https://www.futurlec.com/Transistors/2N5088.shtml 

[saint44]

very cool!! ... so my pin direction is right then (ECB) .. flat side facing the diodes .. im trying to be patient.  noticed you have an MXR Dist + .. me too , love it ... i had to re-build mine ... replaced on the parts and used an LM833 IC instead as well as put 1N34 in series with a 1N4002  for each diode position ... got me a little more volume and gain. ... that wasnt  so frustrating.

[LucifersTrip]

very cool!! ... so my pin direction is right then (ECB) .. flat side facing the diodes

The pinout of 5088 is CBE and the layout is CBE (top to bottom)



you might have 220 instead of 22

[GibsonGM]

very cool!! ... so my pin direction is right then (ECB) .. flat side facing the diodes .. im trying to be patient.  noticed you have an MXR Dist + .. me too , love it ... i had to re-build mine ... replaced on the parts and used an LM833 IC instead as well as put 1N34 in series with a 1N4002  for each diode position ... got me a little more volume and gain. ... that wasnt  so frustrating.

Dist + is the grandfather of a whole generation of distortions )    Move from that to a Guvnor, and you got it made!  That is my "go-to" topology for making good distortions.

Did you make any progress here?  Luc'sTrip's post shows exactly how you should be oriented looking from the top.

[saint44]

ok so i turned the trannies around (CBE),  i had looked at different data sheets and some were EBC and CBE.  here are voltages for both ways .

CBE
Q1 8.98, 2.16, 1.79
Q2 8.47, 1.62, 1.16
Q3 8.90, 8.47, 0.01

flipped back ..

CBE
Q1 8.95, 4.12, 6.91
Q2 1.48, 0.00, 1.28
Q3 2.18, 1.48, 1.47

[saint44]

haven't used the guvnor ... modded my TS5 and used a 3 way switch so i can go between, germanium, silicon, and LED ... i put 4558 and then OPA 2134 for op amp...  those were easy fixes ... but i wanna a fuzzzzzzz from scratch

[R.G.]

When things like this don't make sense, the way to understand is to focus on one time at a time and understand it. The reason the debugging process has you take all those voltages is to force a look at how things are connected - or not.

You're clearly having a problem with pinouts, at least in concept, because you're not understanding exactly which pin is which.  The 2N5088 pinout is as follows: with the flat side facing you, pins down, the pins are from left to right E, B, C. On Q1, the collector pin must be the power supply voltage, and on Q2 the emitter must be at 0V with respect to ground if the layout and PCB are done right.

For an NPN to be amplifying, the collector has to be the highest voltage, the emitter the lowest, and the base about 0.5 to 0.7V higher than the emitter.
[for the fact checkers out there, there are odd special case exceptions, but this is all a beginner needs]

For this to be working, Q2 emitter has to be at 0V with respect to ground. None of your readings have that condition, so either you're reading the pin voltages wrong or your ground lead on the meter is not hooked to ground, or the power supply leads don't go where you think they do.

Here's how to think about unwrapping this problem.
1. Q2 emitter HAS to be at 0V. It's connected to battery (-) by wires and copper traces. If not, you may have the power leads connected wrong (i.e. battery 0V doesn't go to the ground trace); or the meter lead is connected some place other than circuit ground; or the PCB may have a flaw in it, with a short and/or open getting ground to that pin. Notice that this is a statement about the pin going into the PCB and wiring - a simple snippet of wire soldered into the emitter hole of the PCB for Q2 will show this condition.  Until you can get this reading consistently, nothing else is going to come out right. Try removing power and using your meter to test resistance between the wire which carries battery (-) to the PCB and this pin location. If it's not nearly 0 ohms, there is a wiring or board flaw.
2. Once you have solved the mystery of why a pin that's supposed to be grounded is not showing 0V, power the circuit and measure the voltage on the transistors. Here's how to think about this. The base of Q2 simply must be about 0.5 to 0.7V higher than the emitter - which is 0V, so the base will be 0.5 to 0.7V. If it's anything else, there is something wrong with getting bias to the base pin. Could be a board short/open, could be a problem soldering, could be a broken resistor, could be a lot of things, but Q2 base simply has to be about one diode drop high.
3. Once you get emitter and base sorted out, things should start to move along. There's a big problem in how you're getting measurements.

[saint44]

thnx RG .. so here's what i have done

with no transistors at all, at the pin holes for Q1 Q2 Q3

EBC

Q1 0, 4.47, 8.98
Q2 0, 0, 8.67
Q3 0, 8.67, 8.91

i am also getting an ohm reading of 152K at E for Q2 from board ground with no power.   which is right where the 150K resistor is connected to E and then is connected to Q3E, then 220R resistor and then to attack pot.  so basically you are saying that Q2 and Q3 E should be connected to ground same as Q1 E?

[saint44]

rg,

so from Q1E, it should go to ground and also through a cap and 4k7 resistor and then into Q2B and also after the 4k7 resistor (before Q2) it should go to 150K resistor to Attack.  but right now the layout i used has the 4k7 resistor going to Q2B and Q2E going to 150K resistor and then to Q3E. Should i just ground Q2E and from after the 4k7 resistor go to the 150K resistor?  am i being logical?

thnx

bri

[saint44]

thnx Lucifer, Gibson and RG, yeehaaa .. dont know if its logical but that gave me sound, very thin tinny distortion, is that normal,  i have never heard a Jen Fuzz type so not sure what else might be wacked but i do have effect .  are these voltages accurate?

EBC
Q1 6.92, 4.12, 8.98
Q2 0.00000, , 0.60, 1.31
Q3 0.68, 1.31, 5.12

[PRR]

> EBC
> Q1 6.92, 4.12, 8.98

This dis-agrees with R.G.'s teaching.

....the collector has to be the highest voltage, the emitter the lowest, and the base about 0.5 to 0.7V higher than the emitter.

Bad connection from Q1 Emitter to ground is one possible cause.

[R.G.]

Yep.

OK - Saint: this is going to wander around a lot until we get some detailed information.

- There was a schematic and layout posted here. Is that **exactly** what you used?

- If the posted pictures are not **exactly** what you used, you need to post what you did use, or links to them. Links are easiest to post. If you want to post images, get a free IMGUR account, upload the pictures, and put links to them in your replies. Diystompboxes does not let you attach files, only include links to pictures other places.

- Did you (1) buy a PCB, (2) make your own PCB, or (3) build it on perfboard/Vero board? The likely failures are different, so we need to know that to help you.

- What kind of meter are you using? Digital multimeter?

As Paul mentions, the voltages and measurements you're getting are odd, and indicate that something is not working. An open emitter on Q2 is possible, as are some other situations.

Mother Nature is very, very, very particular about the Rules. If even one thing is not right, it simply won't work. Worse yet, She makes us guess what the Rules are as we go along, so humans have been writing those down for several thousand years now, getting them wrong, then correcting them when we find a refinement that's needed so we come closer to what She really meant.

[Jdansti]

To post photos:
1) Sign up for one of the photo hosting services such as photobucket.
2) Upload your photos to the service.
3) Copy a photo's direct URL from the service.
4) Start a message on the forum and click the photo icon (3rd from left above the emoticons).
5) You'll see {img}{/img} in the text, except the brackets will be square. Paste the photo's URL between the two sets of brackets.
6) Alternately, you can type the img code above and paste the URL.
7) If the photo is enormous when you hit the preview button, insert a "height" command to limit the size as follows: {img height=375}your URL{/img}. Play with the height number until you get what you want.

It's much simpler in practice than it seems when reading the instructions. Click on the quote button of LucifersTrip's post above to see how he inserted the schematic.

Welcome to the forum and good luck!

[saint44]

ok, i know Q1 voltages are not right, i was happy to get sound, i know there is more to do.
i am posting pics of what i used, PCB i made myself from the attached.
when you had said Q2 emitter has to be zero, it made sense to me which is why i looked at the schematic again and noticed where the 150K resistor was compared to the schematic.  in the schematic it starts after 4k7 and before Q2 and connects to Q3 emitter after the 220R resistor.  on the layout diagram the 150k connected from Q2 emitter to Q3 emitter (not grounded as in schematic).  so i disconnected the one end of resistor to before Q2 B. (the grey wire).

https://www.dropbox.com/s/fvgxv4a8ckj8p1h/Jen%20Fuzz%20III%20back%20close%20up%20%281%29.jpg
https://www.dropbox.com/s/iyjm7h1tikegttr/Jen%20Fuzz%20III%20P%20Brant%20layout.jpg
https://www.dropbox.com/s/2w05w1vh1t9bazz/Jen%20Fuzz%20III%20top%20close%20up%20%282%29.jpg
https://www.dropbox.com/s/w311f2tw4q4thbs/Jen%20Fuzz%20III%20top%20wiring.jpg
https://www.dropbox.com/s/qti3twy9hy0sqvm/Jen%20Fuzz%20top%20view%20ground%20change.jpg

[saint44]

sorry, to answer your other questions RG, schematic is what lucifer posted, layout was different, digital multimeter. 

[Jdansti]

Based on the BC239C datasheet, the transistors are reversed on your board.



I haven't had a chance to verify your PCB layout against the schematic, but I'll try to do that this evening. Below is an all-in-one glance at the both sides of the board, the wiring, and the layout. I don't see anything glaring with the soldering or wiring.

[PRR]

> If even one thing is not right, it simply won't work.

An Optimist would point out that it may "work"---

> ok, i know Q1 voltages are not right, i was happy to get sound
> very thin tinny distortion

If he gets a gig for "very thin tinny", he's golden. "It works for that!"

Since it is a jacked-up Fuzz Face, I suspect it should be PHATT, an "oh WOW!" sound, classic angry monster killer bees After he does any 'thin tin' gigs he can work more to find the flub(s).

> schematic is what lucifer posted, layout was different

This is a popular way to add mistakes, DIY lay-out.

You know you "can" build directly ON a schematic? For simple well-drawn schematics it may be the shortest path to a working build.

Schematic may have on-board and off-board stuff all the same, and ground/B+ may be symbol implied rather than explicit. Mark-off the off-board stuff. Mark where it connects. Mark-up the long wires. Mark-up the B E and C legs!

Print schematic. Glue to cardboard. Poke holes for part leads.



Insert parts. Bend-over leads toward where they will go. Trim excess. Pre-Tin each lead to get fresh flux/solder on it. Bend leads so they touch. Hit with solder and iron just long enough to get a joint that won't break when you poke it. Many connections can be made with part-leads. Use wire for longer runs.

This won't be the most compact layout possible. Depending on your butt-solders, it may not survive your World Tour. If it gets damp it will act funny. But it is simple and direct and WILL work on the bench and around the house.