Problem w/ bazz fuzz [UPDATE: FIXED AND A CLIP!]

[robotboy]

OK, this is embarassing, but I can't seem to get my freshly built and incredibly simple bazz fuzz to work. I plugged it in to test it, and I could hear the effect sputtering through intermittently, but I couldn't get a solid signal to sustain. I'm testing using a protobox that's already proven to work correctly, so I know it's not the switch or the jacks. When bypassed, everything sounds fine. I broke out the audio probe, and I could get solid signal until I hit the collector of the MPSA13 transistor. Once the probe touches it, the weird sputtering starts. BTW, the transistor is socketed, so I know it didn't get too much heat from the soldering iron. I thought I might have burned out the 1N914 diode, so I desoldered it and replaced with a fresh one while using a heat sink to prevent burnout. Same problem... ugh. I tried to be prudent about not applying too much heat to the pot either, but the probe tells me that it's something related to the transistor. I've tried swapping with another MPSA13, and I get the same problem. My soldering looks ok, but I scrapped in between close connections with a safety pin to be sure. Anyway, I'm burned out, so I"m putting it down for the night. Any suggestions on what to try when I regain motivation would be greatly appreciated.

[vortex]

Have you tried reversing the diode?

[robotboy]

I tested it on a breadboard to see which side accepted signal, so I'm pretty sure it's oriented correctly, but I'll try switching it just in case. Thanks for the reply.

[robotboy]

Anybody else have any ideas?  

[David]

I tested it on a breadboard to see which side accepted signal, so I'm pretty sure it's oriented correctly, but I'll try switching it just in case. Thanks for the reply.

Tested what?  The entire circuit?  If the circuit worked on breadboard,  make sure that both the transistor and any diodes are oriented properly.

But first, a review of "what to do when it doesn't work" might be in order...

[robotboy]

I tested it on a breadboard to see which side accepted signal, so I'm pretty sure it's oriented correctly, but I'll try switching it just in case. Thanks for the reply.

Tested what?  The entire circuit?  If the circuit worked on breadboard,  make sure that both the transistor and any diodes are oriented properly.

But first, a review of "what to do when it doesn't work" might be in order...

Sorry, that wasn't very clear... I tested the diode on a breadboard.

1.What does it do, not do, and sound like?

When engaged, it sputters out signal very intermittently. Bypass works.

2.Name of the circuit = Bazz Fuzz

3.Source of the circuit (URL of schematic or project)

http://home-wrecker.com/bazz.html

4.Any modifications to the circuit? Y or N

Nope

5.Any parts substitutions? If yes, list them.

Nope. I built rev 2 w/ MPSA13 transistor and 1N914 diode

6.Positive ground to negative ground conversion? Y or N

Nope

I'll have to get to step 7 when I get home with my multimeter. I'm going to put another socket on the board where the diode goes, so I can make sure the orientation is correct and also insure that I haven't burned it out by placing a new one in the socket. Thanks for the reply.

[David]

He ran it down by the numbers!  Nice work!  OK, we've established your diode's good and bypass mode works.  Now, as you stated, you need to confirm that:

a) your transistor actually works
b) you have it oriented correctly in the circuit

Take a good hard look at your power connections.  The "sputtering" kind of sounds like a bias problem.  That happened a while back when I was building a FF workalike.

[robotboy]

He ran it down by the numbers!  Nice work!  OK, we've established your diode's good and bypass mode works.  Now, as you stated, you need to confirm that:

a) your transistor actually works
b) you have it oriented correctly in the circuit

Take a good hard look at your power connections.  The "sputtering" kind of sounds like a bias problem.  That happened a while back when I was building a FF workalike.

Thanks for all the help! I'll keep you guys posted as to what happens. This thing is simple enough that it's gotta be fixable.

[David]

He ran it down by the numbers!  Nice work!  OK, we've established your diode's good and bypass mode works.  Now, as you stated, you need to confirm that:

a) your transistor actually works
b) you have it oriented correctly in the circuit

Take a good hard look at your power connections.  The "sputtering" kind of sounds like a bias problem.  That happened a while back when I was building a FF workalike.

Thanks for all the help! I'll keep you guys posted as to what happens. This thing is simple enough that it's gotta be fixable.

If it's totally futzed, debug it by building the entire circuit on breadboard and getting it operational there FIRST -- then build it on your permanent board of choice.

Oh, and don't forget to post voltages.  That'll be the next step.  Do you have an audio probe?  You'll be needing one soon.

[Joe Davisson]

Try:

-Put a large (1M - 2.2M) resistor parallel with the diode, so the transistor remains biased.
-Put a large resistor from base to ground, so the diode will be in conduction, thus biasing the transistor.

It's been a while but I remember having a similar problem when I breadboarded it.

[robotboy]

Try:

-Put a large (1M - 2.2M) resistor parallel with the diode, so the transistor remains biased.
-Put a large resistor from base to ground, so the diode will be in conduction, thus biasing the transistor.

It's been a while but I remember having a similar problem when I breadboarded it.

Do both of the above or just one or the other? Also, I went through and cleaned up all my soldering this morning, and the problem persists; however, I did discover one thing that is VERY ODD. If I select the neck pickup on my guitar, the fuzz works 90% of the time and sputters the other 10% (almost usable :|). On the bridge pickup, the fuzz sputters 98% of the time with just a tiny bit of fuzz getting through. It's not just my guitar either. I've tried it with 2 guitars with the same results... One other question: if the bias is messed up, is that something I did? If not, why wouldn't the above mentioned resistors be included in the schematic? Thanks to everyone for all the very helpful suggestions.

[David]

Try:

-Put a large (1M - 2.2M) resistor parallel with the diode, so the transistor remains biased.
-Put a large resistor from base to ground, so the diode will be in conduction, thus biasing the transistor.

It's been a while but I remember having a similar problem when I breadboarded it.

Do both of the above or just one or the other? Also, I went through and cleaned up all my soldering this morning, and the problem persists; however, I did discover one thing that is VERY ODD. If I select the neck pickup on my guitar, the fuzz works 90% of the time and sputters the other 10% (almost usable :|). On the bridge pickup, the fuzz sputters 98% of the time with just a tiny bit of fuzz getting through. It's not just my guitar either. I've tried it with 2 guitars with the same results... One other question: if the bias is messed up, is that something I did? If not, why wouldn't the above mentioned resistors be included in the schematic? Thanks to everyone for all the very helpful suggestions.

Two guitars with the same results?  Excellent test!  That rules out the guitar.  Now, how are you listening to it?  An amp, I assume?  Are you certain that's working properly?  It probably is, but you have to be able to rule out all possible causes.  OK, if it's not the guitar or the "amp", let's check the battery.  Are you getting at least 8 to 8.5V from that?  You are?  OK, good.  One thing I don't remember:  did you socket your transistor?  If not, you could have heat-damaged it.  Next, let's have those voltages.  That may tell us something.  Have you done continuity checks on it yet?  Yes?  OK, read up on the audio probe and build one.  R.G's "quick and dirty audio oscillator" could prove useful real soon, also.

[robotboy]

Try:

-Put a large (1M - 2.2M) resistor parallel with the diode, so the transistor remains biased.
-Put a large resistor from base to ground, so the diode will be in conduction, thus biasing the transistor.

It's been a while but I remember having a similar problem when I breadboarded it.

Do both of the above or just one or the other? Also, I went through and cleaned up all my soldering this morning, and the problem persists; however, I did discover one thing that is VERY ODD. If I select the neck pickup on my guitar, the fuzz works 90% of the time and sputters the other 10% (almost usable :|). On the bridge pickup, the fuzz sputters 98% of the time with just a tiny bit of fuzz getting through. It's not just my guitar either. I've tried it with 2 guitars with the same results... One other question: if the bias is messed up, is that something I did? If not, why wouldn't the above mentioned resistors be included in the schematic? Thanks to everyone for all the very helpful suggestions.

Two guitars with the same results?  Excellent test!  That rules out the guitar.  Now, how are you listening to it?  An amp, I assume?  Are you certain that's working properly?  It probably is, but you have to be able to rule out all possible causes.  OK, if it's not the guitar or the "amp", let's check the battery.  Are you getting at least 8 to 8.5V from that?  You are?  OK, good.  One thing I don't remember:  did you socket your transistor?  If not, you could have heat-damaged it.  Next, let's have those voltages.  That may tell us something.  Have you done continuity checks on it yet?  Yes?  OK, read up on the audio probe and build one.  R.G's "quick and dirty audio oscillator" could prove useful real soon, also.

I'm listening with an amp, but I also tested line-in on my laptop with the same problem. I tested the battery right off the bat, and it's reading 8.7V. The transistor has been socketed from the get go, so there's no chance of heat damage. I've tried two separate MPSA13 just to be sure I didn't fry it with static electricity or something dumb like that. I double checked the pinout on the web, and it's oriented correctly. See my first post for the audio probe results. I'm going reprobe though since I've touched up my soldering. I'm definitely going to try the resistor suggestion when I go home because it sounds like that might help. I'm still confused about why bias would be a problem to begin with, but I'm also a newbie, so I need to read more. If the resistor doesn't work, I'll post those pin voltages next. What range should I set my multimeter to when testing them? If worst comes to worst, I can just start over and rebuild, but I'm really curious what would cause this problem, and I'd like to know how to fix it if it comes up again in the future, so I'm going to keep stabbing at this for a while. I can also post a clip of the weird sputtering if that would help.

[vortex]

Have you tried making the Bazz Fuss with a NPN tranny like a 2N5088 and the 100K resistor? I found that this combo worked right off the bat for me and it sounds very good.

[robotboy]

OK guys, captain idiot here... I kept checking that my diode was oriented properly by putting it on a breadboard. Being new to this and generally absent minded anyway, I kept making the assumption that electrons flow from positive to negative. Doh! While testing a new diode on my breadboard this evening, I had a eureka moment when I remembered that they flow from NEGATIVE to POSITIVE. Well, I promptly changed the orientation on the bazz, and BAM! IT WORKS!!!! It sounds fantastic too! Anyway, I'd like to thank everybody that helped me figure this out. This bazz clip goes out to all of you. I'm not much of a soloist, but this thing made me think of the blues  and feel like wanking for some reason... Also, I recorded it line in, and I'll say that this pedal sounds 100 times better through my amp, but fug it...

New Favorite Pedal - Bazz Fuzz!!!

Now onto the sparkle boost...

[David]

Okay, people!  He's hooked!   :twisted:

[Ge_Whiz]

Well, that's one of the best adverts for the Bazz that I've ever heard.