Hello all.
I'd really appreciate some help with my build please, if possible. I have followed the troubleshooting steps in the FAQs but nothing seems to have had any effect. This is my first build with a PCB rather than a veroboard which I though would be more straightforward. That was certainly the kiss of death!
The kit is the Supreme Compressor from Effect Pedal Kits. It is based on the Valvewizard Engineer's Thumb, with 4 control knobs.
A lot of fuzz-like distortion is being produced when the input signal is higher, i.e. when a string is played hard. Sounds ok when played gently. Exhibits the behaviour with both humbuckers and single coils. Can be reduced by playing with the vol and ratio pots but not removed entirely. Sounds as though when trying to compress it is distorting instead. Bypass works fine.
Schematic:
No modifications to circuit or parts subs.
Battery voltage 9.02V
Voltage at the circuit board end of the red battery lead = 8.88V
Voltage at the circuit board end of the black battery lead = 0V
For the following, vol, attack and threshold turned fully clockwise, ratio turned fully anticlockwise. From looking at these, my instinct is that the problem is to do with U2:B function, but I quickly reach the limits of my understanding at this point!
Q1
C = 1.08V
B = 4.80V
E = 4.41V
U1
5.23V
4.45V
3.98V
0V
4.17V
4.43V
4.43V
8.83V
U2
1.08V
30mV
4.42V
4.42V
4.44V
0
0
0
100mV falling
0
8.82V
0
0
0
0
0
U3
4.46V
4.45V
3.98V
0
4.21V
4.45V
4.86V
8.83V
D1
A = 4.21V
K = 4.45V
D2
A = 4.46V
K = 4.46V
D3
A = 4.84V
K = 4.45V
Any pointers very much appreciated!
Supreme Compressor (Engineer's Thumb) Distortion
- Manfred
- Tube Twister
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