Troubleshooting Fur Face Clone

[kiltedyak]

Hi Guys,

I am a complete newbie building a a Fur Face from Small Bear Electronics. Here is a link to his awesomely detailed how to http://www.smallbearelec.com/Projects/FurFace/BeginnerInst.pdf.

My issue is that whenever I engage the circuit, the guitar tone becomes attenuated instead of amplifed and fuzzy. I can hear the guitar and the tone and level pots appear to be working, but there is absolutely no change in the sound when I turn the fuzz pot. I have checked the voltages at the transistors and they seem pretty close to dead on to what the instruction say to expect.

pics
https://picasaweb.google.com/lh/photo/1UNMLo_l9_IDaVrCHPSBQQ?feat=directlink
https://picasaweb.google.com/lh/photo/hh4v5uxYwwLvo8kWG3JjGw?feat=directlink

Thoughts?

[R.G.]

Debugging: what to do when it doesn't work

[kiltedyak]

OK Fair enough

1.What does it do, not do, and sound like? Bypass works fine. When circuit engaged the volume of the signal is lessened and there is zero fuzz or distortion sound. Working the fuzz pot stop to stop results in no change in sound. Working the tone pot stop to stop results in expected frequency profile change. Working the volume 100% will drive signal to zero, but even at the loudest, the signal is less than when bypassed.
2.Name of the circuit = FUR FACE (Small Bear)
3.Source of the circuit (URL of schematic or project) = (See link to PDF, schematic 3rd page from bottom, Trans voltages 5 or 6 pages up from bottom)
4.Any modifications to the circuit? N
5.Any parts substitutions? N
6.Positive ground to negative ground conversion? N
7.Turn your meter on, set it to the 10V or 20V scale. Remove the battery from the battery clip. Probe the battery terminals with the meter leads before putting it in the clip. What is the out of circuit battery voltage? =>9.51 (DC Adaptor)
Now insert the battery into the clip. If your effect is wired so that a plug must be in the input or output jack to turn the battery power on, insert one end of a cord into that jack. Connect the negative/black meter lead to signal ground by clipping the negative/black lead to the outer sleeve of the input or output jack, whichever does not have a plug in it. With the negative lead on signal ground, measure the following:
Voltage at the circuit board end of the red battery lead =9.51
Voltage at the circuit board end of the black battery lead = 0

Now, using the original schematic as a reference for which part is which (that is, which transistor is Q1, Q2, etc. and which IC is IC1, IC2, C1, and so on) measure and list the voltage on each pin of every transistor and IC. Just keep the black lead on ground, and touch the pointed end of the red probe to each one in turn. Report the voltages as follows:

Q1
C =1.6
B =.67
E =0

Q2
C=4.76
B=1.6
E=.96

D1
A (anode, the non-band end) = 9.5
K (cathode, the banded end) = 9.32

For the fuzz pot I measure .96 -> 0 volts off the center lug as I rotate the pot 100%

The volume, tone, and LED circuits seems to be working fine, but I can gather any data points you guys want.

[smallbearelec]

I have replied privately. One thing that my instruction manual was missing was an "X-ray" layout drawing of the PCB to use in doing continuity testing. I generated that in about two minutes from the Eagle file, have sent it to the customer and will include it in a revised manual.

SD

[kiltedyak]

Steve's advice got me thru.

For those who were anxiously awaiting resolution... If you guessed cold solder joint at the capacitor at the fuzz pot you are a WINNER!