Hely guys,
I built an Engineer's Thumb compressor on vero (same one in this thread)
http://www.madbeanpedals.com/forum/index.php?topic=6206.0
and am having some problems. I have built about 40 boards now (a dozen or so on vero) and have managed to get them all to work so I am not a total noob and have ruled out the obvious. I am getting a LOT of noise and the pedal doesn't seem to be compressing. There is a constant hum/buzz and with all the knobs staight up the volume is almost double that of my original signal. Here is what happens when I turn the knobs:
Vol- works as normal.
Attack- Rumbles when all the way down.
Ratio- acts like a volume control.
Release- cuts the signal off like a switch when turned all the way down.
Threshold- cuts the signal off like a switch when turned all the way up.
I did notice that some of the voltages on IC2 jump around a bit (pin 2 and 4 are the worst). I don't get absolute 0.00 on pin 4 of IC2 so maybe that's the problem?
Here are my voltages:
IC1- 5.30, 4.58, 4.38, 0.01, 4.38, 4.59, 4.59, 9.17
IC2- 4.80, 4.70, 4.62, 0.15, 4.58, 4.60, 4.70, 9.18
IC3- 1.10, 1.52, 4.61, 4.59, 4.58, 0.00, 1.36, 1.96, 0.00, 9.18, 1.31, 0.82, 0.82, 1.10, 0.21
Q1- C-1.08, B-4.61, E-4.58
I examined the board with a magnified light and don't see any unwanted traces or jumps anywhere. I also tried replacinging the IC's but no change. Any suggestions would be greatly appreciated!
You've got a jumper wrong on the OTA. Pin 11 should be your supply voltage, not pin 10.
Voltages on IC 1 and 2 look ok. You should have zero at ground, but you don't quite.
Have you verified there's no solder bridges or wrong part issues?
Jacob
Quote from: midwayfair on April 14, 2013, 11:16:29 PM
You've got a jumper wrong on the OTA. Pin 11 should be your supply voltage, not pin 10.
My bad. I only listed 15 voltages! Pin 11 is actually source voltage.
IC3- 1.10, 1.52, 4.61, 4.59, 4.58, 0.00, 0.01, 1.36, 1.96, 0.00, 9.18, 1.31, 0.82, 0.82, 1.10, 0.21
Quote from: jkokura on April 14, 2013, 11:16:40 PM
Voltages on IC 1 and 2 look ok. You should have zero at ground, but you don't quite.
Have you verified there's no solder bridges or wrong part issues?
Jacob
Yeah I was wondering if that 0.15 could be the problem. I checked pretty well for unwanted solder bridges. I will double check components again.