Fuzz and germanium trans help

[roccster]

Ok folks, i need some help.

Im trying to build the Bonamassa Fuzz Face posted at: http://tagboardeffects.blogspot.se/2014/07/dunlop-jbf-3-joe-bonamassa-fuzz-face.html

First I had some issues with the whole pos. ground wiring. So for test I hooked up a couple of silicon transistors. Wired with pos. ground the pcb is dead quite, but if I switch the polarity to neg. ground it´s starts to Fuzz, not great but at least it´s making a sound.
I didn´t mind this at first since I was waiting for the germanium transistors (MP39B) anyway. Last night I got the transistors and hooked em up.
First I tested the HFE in my multimeter. The transistors is at 60 (some more some less), i did this to make sure that I got the right legs (CBE) for the right socket in the PCB. I then hooked them up in the PCB, connected my negative voltage inverter for pos. ground to the PCB and turned it on.
Dead quite, not a sound. The bypass signal is ok.

I meassure the output of the inverter and it is -8.6V.
I meassure the transistors and make sure they get some juice and get several readings.

Can´t get my head around this so i turn the transistors 180 degrees basicly hooking them up "wrong" and then I get some signal through, not alot though and barely any fuzz, just a really low signal.

I have checked and rechecked the PCB and just cant find what is wrong. Any ideas? What more can I do to troubleshoot?

Thanks!

/ Richard
 

[roccster]

Found this article and will run through this when I get home:
http://www.geofex.com/fxdebug/newfx.htm

any other comments are appreciated

[Thecomedian]

Something that has always helped me when I get stumped is redrawing the schematic by following the parts and connections. Is it actually a PCB, or is it perf/vero? If it's vero, then it could be missing a trace cut.

[roccster]

Sorry, it´s a veroboard as in the article from tagboardeffects.

[roccster]

Forget that, i looked wrong. All cuts are there.

[roccster]

Ok, went back to the project.

Rewired the off-board as guitar fx suggests: http://tagboardeffects.blogspot.se/2012/02/offboard-wiring.html
Hooked it up to my inverter
Verified all wires going to the breadboard

Now I am making some progress. I finally got some life (and fuzz) signs out of the ger. transistors, but the values seems off. Also there is a really high pitch squeek in the background (vol and fuzz at max).

Ok the readings from the transistors:

Q1
C: -0.690v
E: -112mv
B: 0

Q2
C: - 4.7v
E: 0.600v
B: 0.700v

/ Richard

[smallbearelec]

Q1
C: -0.690v
E: -112mv
B: 0

Q2
C: - 4.7v
E: 0.600v
B: 0.700v

Presuming you are measuring correctly, the Base of Q1 at O V says that something is definitely not right. IMO, you should breadboard this and make it work there before trying to commit to solder. You said that you are using an inverter?? More detail on that, pls. I would suggest powering with a battery so that you know exactly what is being fed to the effect. For purposes of getting it working, a battery eliminates a lot of possible problems with noise.

[roccster]

Yep that's exactly what I'm doing now. I have bread boarded the pedal and the battery is hooked up to the inverter: http://tagboardeffects.blogspot.se/2012/05/negative-voltage-inverter.html
That way I know I get pos ground, also it prepares the pedal for the board later on IF I can get it to work.
But looking at the layout doesn't ground connect directly to Q1 emitter? Then it have to be 0 right?

I suspect that there is a ground issue some where. Bypassed the signal is quite, but activated it starts to hum and hiss...
Thanks for feedback!

Rgds
/ Richard

[Thecomedian]

Can you take the inverter out and plug the battery + direct to ground and - direct to the resistors that feed the collectors, and see if you get any change?

Yep that's exactly what I'm doing now. I have bread boarded the pedal and the battery is hooked up to the inverter: http://tagboardeffects.blogspot.se/2012/05/negative-voltage-inverter.html
That way I know I get pos ground, also it prepares the pedal for the board later on IF I can get it to work.
But looking at the layout doesn't ground connect directly to Q1 emitter? Then it have to be 0 right?

I suspect that there is a ground issue some where. Bypassed the signal is quite, but activated it starts to hum and hiss...
Thanks for feedback!

Rgds
/ Richard

I think 0v base means the b-e junction is in cutoff and the voltages you are seeing on C and E are coming from leakage current along with internal transistor resistance.

Do you have an electrical wiring schematic as well as the vero design?
http://s378.photobucket.com/user/mmolteratx/media/JBFuzzFace.png.html

with the Q1 collector variable resistor (usually a pot wired that way), 33k resistance is the old fuzz face resistance between battery and Q1. You might try turning pot down to zero and then slowly edging back up to see if you start getting some voltage for the base. Q1 collector should be around 1.2v, maybe a little higher, as a baseline to work from. Nevermind, I see the one you're using does not have varistors between collectors and -9v.

You said you get a high pitch squeak, and the inverter comments say that can happen with that chip unless it's in "boost mode" which is why I suggest removing it and going battery only. If this is the only problem, it's half solved and you can fix the inverter  

[duck_arse]

that vero layout shows q1 as "c - b - e" and q2 as "e - c - b", top to bottom. any chance this is confusing yr readings/writings?

[roccster]

Ok folks,

I gave up on all this mess with pos. ground and did another fuzz instead (neg. ground and silicon transistors):
http://tagboardeffects.blogspot.se/2014/07/joe-davisson-antiquity-fuzz.html

My guy at the electronics store didn´t have the 2N5089 trans so he gave me BC169 instead.
I built the layout and placed these transistors in their slots and the pedal is dead quite (when activated). So I troubleshooted like a mad man and today I gave up and swaped the transistors with these:

Q1: 2N3904
Q2: BC239C

And BAM the pedal is alive! Some serious fuzzing going on, and some other noise (everything is hooked up in the breadboard atm).
Changing these resistors, especially Q1 have major inpact on the ammount of fuzz going on.
So are the BC169 that "weak" and if so, what shall I replace to get it to work with the BC169? Original Fuzz Face have 33k resistor to Q1 if I remeber right, but this layout have 100k.

Also, do you think it is possible just to reverse polarity to get a pos. ground and replace the transistors with ger. transistors?

Sorry for these noob qs but im learning...

[roccster]

Ignore that about the BC169B, I found the datasheet and noticed that the suckers have E C B not E B C as the other transistors

[allesz]

Hey. If you want to try positive ground just reverse the connection from your battery/power supply and the breadboard. Of course you will have to reverse (flip) the electro caps.

[roccster]

Hey. If you want to try positive ground just reverse the connection from your battery/power supply and the breadboard. Of course you will have to reverse (flip) the electro caps.

Thanks m8,
Flipping the caps was one of the things I was wondering. What about the diodes?

Back to soldering  

[allesz]

You are right about diodes... but the bonamassa ff has no diodes. If you speak about reverse Voltage protection diode, it must be reversed.

[roccster]

You are right about diodes... but the bonamassa ff has no diodes. If you speak about reverse Voltage protection diode, it must be reversed.

Great, i was referring to the Antique Fuzz in this case (since thats the one working atm)

Thanks again!

[allesz]

Ha ok, if you are talking about Joe Davisson Antiquity fuzz I think you will have to reverse the input diode.

[roccster]

Here´s another Q for ya.

I mannaged to build the Joe Bonamassa Fuzz Face, and it´s fuzzing allright. One thing that I find a bit strange is the way the Fuzz pot works. At full there is plenty of fuzz but by just rolling it back a little most of the fuzz goes away.
Layout here: http://tagboardeffects.blogspot.se/search?q=bonamassa
Any thoughts on that?
I built it with MP39b and GT308b transistors.
Was thinking of maybe swapping one of them out for a AC128 maybe...

[italianguy63]

Pretty typical.  Expecially if the trannys have lower Hfe's.  Usually, the fuzz knob stays pretty cranked.  Rolling the guitar pot back to 7 or so, will chill it way down too.

MC

[roccster]

Pretty typical.  Expecially if the trannys have lower Hfe's.  Usually, the fuzz knob stays pretty cranked.  Rolling the guitar pot back to 7 or so, will chill it way down too.

MC

That´s spot on whats happening Guess thats why Joe runs it cranked.
Well gonna build another Fuzz with silicon transistors and see how that sounds.

It´s not that the J.B Fuzz sounds bad. It´s really warm and fuzzy, just that I would like to have a little bit more versatility in the pedal.