SOLVED Low Tide BBD works but doesn't modulate

[inflatablerobot]

Thank you for considering my issue.
I am getting no modulation of the BBD, howeveer I can hear the BBD chorusing when manually turning the Depth knob.
So the BBD passes through audio and the low pass gate functions as expected.
The ATtiny is outputing random voltages on Pin5.
Pin3 of the MCP602 is getting the random voltage from the ATtiny.
Pin1 and Pin2 of the MCP602 have continuity, so it should be buffering in input on Pin3.
The output of the MCP602 on Pin1 is holding at a constant 0.9V.
This is what is baffling me, why is the output of the buffer not moving along with the input?

Any help you might provide would be greatly appreciated.

I am working off the schematic found here

Here are the troubleshooting steps I've taken.
-insure pots isolated from board with capton tape and air gap, not in a enclosure
-insure MCP602 and ATtiny are getting 5v supply from regulator
-confirmed ATtiny is outputing random voltages between 0-5V on pin5 (I can share the code if interested)
-swapped new ATtiny chip, new MCP602 opamp, BBD, and CD4046
-insure continuity between various connections to rule out broken trace(s)

 

[LukeFRC]

If the thing is chorusing that’s what it’s deposed to do? Turn the skew fully counter clockwise and it becomes more random

 

[inflatablerobot]

Oh I guess I wasn't clear. The BBD time is not being modulated. If I turn the amount knob I can manually modulate it and hear chorusing, but only while I physically turn the knob since the modulation portion of the circuit isn't working correctly.

It's strange to me, as the ATtiny is producing the random voltage but the MCP602 op-amp that is supposed to buffer that voltage coming from the ATtiny just sits at 0.9V whereas it should output exactly what is coming in. That op-amp seems to be the problem, but I've swapped it out and it behaves the same. I think I ordered my MCP602 chips from Tayda, so I guess they could be fakes maybe. Maybe I'll put in an order at Mouser and see if that makes a difference.

 

[LukeFRC]

I was going to write something about the circuit but you've covered most of my thoughts... I guess MCP602 is getting the right power?

Generally for testing.... It's a subtle effect- I find it easiest to hear with mix all the the way up, LPG all the way clockwise, slew down and rate half way - that way you are listening for a random vibrato which should be easy to hear!

the only other thing I would suggest - I 've had some bad results with tape to isolate pots from the PCB - strips of card from a cereal box works well

 

[inflatablerobot]

So it turns out both of the MPC602 opamps I got ordered from Mouser were bad. I made a test setup with a variable voltage divider on a breadboard, powered it at 5V, and set up a simple buffer on both sides of the opamp. Neither chip could properly buffer any voltage I feed it. I tested a TL072 in my little setup just as a sanity check, and it worked as expected. I figured since the modulation signal coming from the ATtiny Randomizer chip is pretty slow I should try the TL072 in place of the MCP602, as both opamps have the same pinout and the TL072 can run just fine at 5V. And now my pedal works.

And to think, I had previously thought I fried my ATtiny chip so I went through the trouble of getting a programmer and coding up my own random modulation sketch just to find out later it was just an opamp that was dead.

Anyhow, the pedal sounds awesome. I especially love running fuzz through it.