Help with Analog bit crusher

Started by Heemis, March 01, 2009, 04:26:19 PM

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Heemis

So I'm working on this circuit:  http://experimentalistsanonymous.com/diy/Schematics/Fuzz%20and%20Fuzzy%20Noisemakers/Analog%20Bit%20Crusher.gif

I breadboarded it, made some modifications, and I just finished putting it on perf.  I hooked it up to test it before putting it in it's enclosure and I got signal through the input and output buffers, but no change when I rotated the frequency knob.  This leads me to believe something went wrong with the oscillator.  I had some trouble using the original values on the schematic, so according to other posts, I changed the resistor going from the + input of X3, to the output of X4 to 47k, and the resistor going from the two diodes to the JFET to a 470k.  These worked just fine on the breadboard.  I plugged the unit in and took some readings:

IC 1 (input and output buffer)
P1: 4.66
P2: 4.66
P3: 2.28
P4: 0
P5: 4.66
P6: 4.66
P7: 4.66
P8: 9.32

IC 2 (Oscillator)
P1: 8.63
P2: 4.44
P3:  This one is strange, when I touch the multimeter probe to it, the audio cuts out, and I have to unplug the power and plug it back in to get it to work.  Also, once the audio goes out, voltage starts to climb from 1.3 to around 3.3 before I took the probe away. 
P4: 0
P5: 4.44
P6: 8.26
P7: 1.34
P8: 9.32

Q1:
D: 4.66
S: 4.66
G: 5.21

I really can't think of what is wrong.  I rechecked all my solders and they look fine.  I'm thinking maybe I burned out a diode?  I tried replacing the ICs and FET and neither worked.  Please help!!  Thanks.

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Heemis

Ok, I figured it out... wired the 47k resistor to the wrong side of the 100k...  :icon_redface:

Anyway, for anyone who's thinking of building this circuit, it's very fun for use on drum machine.  I converted the first buffer to an amplifier with a gain of ~30 to boost the incoming signal, and also added a "freakout" switch which cuts the connection between the op amp's output and the gain pot, very fun for those tweaked out electronic sounds.