Overdrive pedal drive knob problems

[JohnRhodes]

Hey there! I recently built a Colorsound Overdriver following the http://tagboardeffects.blogspot.co.uk/2012/09/colorsound-overdriver.html layout.

1. My problem is that the drive pot only really does anything at the very end of the taper, the sound is non-existant when the drive is low or down, clean in the middle and then all of a sudden is fuzzy. There's no overdrive in the middle, and the volume is very low until the very last portion of the taper. The pot is a 10k linear pot as suggested by the guy on tagboardeffects. I've heard that Colorsound Overdrivers are supposed to be fuzzy at max though. Anyway, something must be wrong.
2.Name of the circuit = Colorsound Overdriver
3.Source of the circuit (URL of schematic or project) = tagboardeffects
4.Any modifications to the circuit? No
5.Any parts substitutions? No
6.Positive ground to negative ground conversion? No
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? => 7.5v (I measured the battery, is that right?)
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 = I don't understand where to measure
Voltage at the circuit board end of the black battery lead =I don't understand where to measure

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 =3v
B =1v
E = 1-1.5v

Q2
C=6v
B=3v
E=6v

Q3
C=2v
B=1-2v
E=1-2v

Here are some pics!


Thanks in advance!

[Jdansti]

1) Check the board for solder bridges using a magnifier. If necessary, try running a razor knife between each row of copper. 
2) Get a fresh battery.
3) Re-measure the voltages with the fresh battery.

[JohnRhodes]

1) Check the board for solder bridges using a magnifier. If necessary, try running a razor knife between each row of copper. 
2) Get a fresh battery.
3) Re-measure the voltages with the fresh battery.

Yeah I checked the board for solder bridges using a multimeter, also did the knife treatment.
Gonna see if I can get my hands on a fresh battery today or tomorrow. Could I use a 9v adapter or does it have to be a battery?

[Jdansti]

A regulated 9v adapter would work. If its not regulated, check the voltage before using it. I'm not sure how high you can go on this effect, but if you're <10v, you should be OK. Also make sure you connect it using the correct polarity.

[pinkjimiphoton]

no, i don't think there's anything wrong. to really get fuzz out of one of these, you pretty much have to peg them, and there's a dead area when turned down, and then it doesn't really do much other than add volume til the top of the sweep. it was meant to be a power boost, not a fuzz. if you WANT fuzz, i'd suggest adding a master volume to it, cuz other wise it's pretty much just a clean boost that pummels your amp. adding a master volume, you can dime the gain control and control the volume to reasonable levels, and get fuzz...kinda.
it's meant more to destroy the input stage of your amp, than to actually cause distortion..it's a TRUE "overdriver", meant to push an amp into distortion.
if ya want it to be a fuzz, try tacking a diode clipper on between the circuit side of the output cap and ground.

[midwayfair]

Jimi's right. The circuit does this. In fact, most gain controls on the emitter of a transistor do this. The gain increases far more between 300 ohms and 0 ohms than it does between 300ohms and 1K. You can get more fine adjustment out of the higher settings on the drive pot by using a reverse audio taper.

[pinkjimiphoton]

or hit radio shack or whatever, get a 500r pot, and add a 470r resistor in line with it.

[JohnRhodes]

Alright. I think I'll t try replacing the drive pot with a 5 K reverse log pot and enjoy the pedal meanwhile! Would you say a 5K reverse log pot would be a good value?

[pinkjimiphoton]

hi john,
i forget what's in this circuit, but yah, if it's supposed to be a 5k linear, a 5k reverse log will probably be great.

i just got mine back...i'd given it to a friend, who loved it... but he decided he didn't want to deal with anything more than what's on his pedalboard, so i'll see if i can look into this a little myself.
rock on!