Bazz Fuss no longer fussing - NOW WITH DATA!

[spacetimc]

I followed the debugging checklist. Here's the information:

Bazz Fuss

When I built the circuit, it worked fine. Great gnarly fuzz with ugly decay. Worked well for a couple of months. A few days ago, it started sputtering. I thought maybe the battery was dying, so I inserted a new 9v. Suddenly, I had a clean boost - no fuzz at all!

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

Here is the schematic: http://www.home-wrecker.com/bazz3.png

I worked with this perfboard layout: http://www.home-wrecker.com/bfv1-perf.png

As recommended on the page, I socketed the caps, diode and transistor. The input cap is 4.7uF, the output cap 0.1uF. The diode is a 1N4148. The transistor is an MPSA13. The resistor is 10k. I checked the pinout on the tranny, and it is inserted correctly into its socket.

The circuit is negative ground. i used a digital multimeter to run the measurements. I also used a fresh battery.

Q1
C = 8.05
B = .532
E = .000

D1
A = .532
K = 8.05

Thanks in advance for any information and help y'all can provide!

[JerS]

I am just taking a shot in the dark to say check the diode connection. Without the diode, the circuit will be a sort of clean boost. I would think that the cathode side of the diode should be the anode voltage minus the voltage drop of the diode (8.05V - approx 0.5V depending on the diode type).

Try to directly solder the diode and see if that fixes it.

Let us know how you do!!

[duck_arse]

your diode voltages suggest the diode is arse-about. K should be same V as B, A should be same V as C.

[ManuVel]

Have you tried replacing the transitor?

[PRR]

Transistor Collector should be at three diodes drops, 1.5V to 2.0V.

(Two 0.6V drops in the Darlington, one in the diode.)

Half-Volt on a Darlington's Base suggests it is dang near turned-OFF, which is not a happy point for audio. You may get a brapp out of it for BIG strums.

If the diode is backward, Collector wants to rise to infinity, but can't quite reach the 9V feeding it.

8V instead of 9V is probably meter-loading. However 8V/9V suggests an 80K or 100uA meter, while most cheap DMMs are over 1Meg. Are you using a needle-meter? That can work, but is good to know.

Remember that a VERY popular mistake is a 100K or even 10Meg where you thought you put a 10K.

[spacetimc]

Thanks, everyone, for your responses!

@ManuVel - I did try replacing the transistor. I discovered my problem a half-hour before band practice (naturally!). I replaced the original MPSA13 with another, with no change in signal. I then frantically tried any other transistor I had in my box of parts, without taking note of what was what. On occasion, I got a fuzz sound but with very little volume. I will test this again, with the DMM.

@duck_arse - I will try turning the diode around, but the pedal was functioning prior to this, with the diode in its current configuration.

@PRR - I am using a needle-meter, if I understand you. It has pointy bits at the end, instead of alligator clips. I double-checked that the resistor is 10k. If the half-volt on the base "suggests it is dang near turned-OFF", what would cause this?

For what it's worth, here's another bit to the puzzle, which may or may not be salient: I have a used Cry-Baby wah which, when used in conjunction with my BazzFuss, emits a feedback squeal. I can control the modulation of the squeal with the wah (much to the delight of my bandmates). Perhaps this combination somehow fried something in the Bazz Fuss?

[duck_arse]

the needle type


the other type


the probes for poking have pointy ends. have you shown us pictures of what you built yet?

[ManuVel]

the probes for poking have pointy ends. have you shown us pictures of what you built yet?

^ It would help to have a picture of what you've done.