Minimoog deadband mod

Hi guys - I have a late osc board Model D and have finally gotten around to installing the deadband mod as per the moog service bulletin/synthfool hand-drawn schematic. After installing everything (including the 619K resistor) the deadzone works but the synth is now about 4 semitones flat! I have double-checked everything as per the factory bulletin and it all looks correct, and the voltage across the diodes is in spec (0v +/- 0.1v). I tried seeing if it would recalibrate but the trim pot maxes out before it can reach pitch so something must be up! If I adjust the pitchbend pot so it is in tune then the voltage across the diodes reads approx. 0.4v and obviously the deadzone no longer works. I’ve been able to remove the mod and the synth checks out OK again, but reinstalling it gives the same problems…Any help would be much appreciated. Thanks :slight_smile: