MXR Phase 90 History file 2015-06-30 - Started History File. 2015-06-30 - Updated the layout with a correct wiring for the pot. We have found that this wiring gives a slightly smoother rotation than the wiring implied by the schematic. We also made some minor corrections to the schematic where some connector "dots" were missing and the power protection diode was not drawn correctly. Also corrected some errors in the voltage readings for Q5.