Brach,
Thanks so much for the detailed response!
Update:
Getting tap LED flash sequence 2-3-6 when performing the start-up hold above. This matches up w/ the slip of paper that came w/ the unit, s/w ver 2.3.6. Good to go I guess.
I checked Y1, C5, and C6 first. Continuity or open where it’s supposed to be against the schematic (Y1 should read open when unit is powered off I assume). Replaced C5 and C6 just in case and remeasured everything.
Checked each pot again, checked voltage across wiper to ground at various positions of the pot’s sweep, verified getting the same voltage reading at their respective pins on the microcontroller (verified at the actual pin on the chip, not just the solder point of IC socket/PCB).
Went back and checked correct component placement again.
Here’s a more detailed set of symptoms:
Power unit up, bypass LED off, tap LED on solid, effect is off, clean sound thru amp. I would assume the tap LEP should be blinking at the rate corresponding to the position of the Rate pot at this point.
Click bypass switch, bypass LED turns on, tap LED still solid, unit still passes clean sound.
Move the rate pot around a little, tap LED shuts off, unit no longer passes sound.
Click Tap switch a couple of times, unit starts passing trem-ed sound and Tap LED shows tapped tempo.
Move Depth pot around, jittery trem-ed pulsed not in time w/ tempo, unit returns to correct trem-ed pulses while not moving Depth pot around.
Move Multiplier pot around, tempo jumps to 4:1, stays there until I tap a new tempo in, which is now pulsing at 2:1 ratio regardless of Multiplier pot position.
Moving Shape pot around does the same as moving Depth around.
Spacing pot works fine (woo!)
Harmonic mix works fine but does cause some jittery pulses during pot sweep.
I have to this there is something wrong w/ 5V voltage divider network forming the inputs for VR1 thru VR6, but they measure fine w/ my meter and I’m not sure how the tap tempo would work and/or be affected by this anyways.
Will probably start pulling pots off and replacing w/ 100k resistors to max/min out certain parameters one at a time to see if I have a weird pot or something that’s causing voltage spikes or something. Or replace Y1. Or buy a pre-made unit and give up on this one!
Truly stumped.