I just replace the diode and the ADSR behavior is different but still not right. The release slider is still just generating a fixed voltage at the ADSR output when I adjust it as well. Thank for the tip on the 2N5460, I'll pull that next and test it after I go through and verify the rest of the components with the unpopulated pcb photo that @fallout helpfully provided.ebfx wrote: ↑Wed Jan 13, 2021 7:23 pmI'm curious to know if this solves your problem. The diode in question is part of the ADSR circuit so I wouldn't expect much effect on the AR operation.
I've been trying to track down a similar problem with my v4 build for a few nights now. After reviewing the v3 schematics and spending a few nights probing my board, I narrowed the problem down to the 2N5460 (Q4) in the ADSR section. I pulled Q4 from the board and put it in my (admittedly very cheap) transistor checker and it came back as a BJT instead of a JFET. So, I replaced both 2N5460's in the ADSR/AR section and everything started working as expected. You may want to check if you have a similar problem.
I checked the markings on the original transistors from Synthcube and they are definitely labeled 5460, so I suspect they either got a bad batch or I was a bit too heavy-handed during installation. My replacement NTE 2N5460's have a different pinout (S-D-G instead of D-S-G) so I had to do a bit of pin swapping on the board, but they read as P-channel JFET's on my tester and now my circuit is working like it is supposed to.
edit: I just pulled a 2N5460 and tested and sure enough it tests as a BJT-PNP as well. i sourced mine from utsource originally. I'll order some replacements and see how it goes. thanks!