Phase II Distortion

Quirkey

Active member
Hey Yall!

Been busy at my normal job so my "night job" of building pedals and posting them has taken a hit.

Thanks to all the helpful comments here and just a steady diet of building and debugging I will say that I've gotten so much better at diagnosing problems. In this case, I have my first attempt at a Phase II and while it seemed to come on and the LED/LDR combos in relation to the pots seem to all work (rate and depth reflected), the signal is a distorted mess.

I _think_ I've tracked it down to the left side of IC1. The right side (pins, 5,6,7) all sound normal, and clear. The left side (1,2,3) sounds like an overdriven, distorted mess. From my read of the schematic, I have a feeling it's something with biasing but this is where I get lost. Should I be looking at R5?

Any thoughts are appreciated!
 

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Hey Yall!

Been busy at my normal job so my "night job" of building pedals and posting them has taken a hit.

Thanks to all the helpful comments here and just a steady diet of building and debugging I will say that I've gotten so much better at diagnosing problems. In this case, I have my first attempt at a Phase II and while it seemed to come on and the LED/LDR combos in relation to the pots seem to all work (rate and depth reflected), the signal is a distorted mess.

I _think_ I've tracked it down to the left side of IC1. The right side (pins, 5,6,7) all sound normal, and clear. The left side (1,2,3) sounds like an overdriven, distorted mess. From my read of the schematic, I have a feeling it's something with biasing but this is where I get lost. Should I be looking at R5?

Any thoughts are appreciated!
1. Clean the Back of the PCB, there is a lot of Flux residue & debris that needs to be removed.
The best stuff I recommend & use is CRC CO Contact Cleaner in a Spray Can!
2. Check for any solder splashes between the pads.
 
OK. Finally had time to pick this back up. Thoroughly reflowed the board, cleaned the back. Still the same deal. I tried swapping ICs, no dice. I removed that resistor (r4) and tested it and it is 4.7K and replaced it. Same. One interesting thing I noticed is that when I tested voltages the charge pump is actually putting out -7.8V not -9V. Not sure if this is the issue but i also tried swapping out the charge pump and it is consistent.

Stumped!

Here's a sample of a loop playing through it (clean first then on, then twiddling the knobs). Listening back it sounds kind of rad(?) but obviously not the intended effect.

 
OK. Finally had time to pick this back up. Thoroughly reflowed the board, cleaned the back. Still the same deal. I tried swapping ICs, no dice. I removed that resistor (r4) and tested it and it is 4.7K and replaced it. Same. One interesting thing I noticed is that when I tested voltages the charge pump is actually putting out -7.8V not -9V. Not sure if this is the issue but i also tried swapping out the charge pump and it is consistent.

Stumped!

Here's a sample of a loop playing through it (clean first then on, then twiddling the knobs). Listening back it sounds kind of rad(?) but obviously not the intended effect.

I’m curious, are the pots the right taper? A linear would do that when it calls for a log.
 
OK, follow up. I think I might have to just ditch this build :( I tried replacing R4, R5, R6 with normal-size 4K7 resistors and still no dice. Its really strange, the signal is completely clear At IC1, pin 7 and to one side of R4. The other side of R4 is distorted. I tried swapping out IC1 as well but same issue. Stumped.
 
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