EH Black Finger V.1

[lowell]

Hey all,
      I'm gonna try in this forum to see if anyone can help me w/ this.  I've replaced the opamp and many transistors in this pedal.  It now works but the "sustain" knob has to be in the "sweet spot".  Could anyone guide me in troubleshooting this pedal?  I guess the opamp is possibly damaged again since I replaced it and have worked on the pedal quite a bit since then, but don't remember any specific times where I though "shoot I probably fried it."  Any help w/ this would be great. 

http://www.drfretgood.com/blackfinger748ic.pdf