Wierd question I know.... involves an older (1996) Hitachi 5.7" color LCD (Hitachi LMG9520RPCC-A, on a CNC router control) that for some reason used negative voltage (pin 7, VEE power supply for LC) but it's closest Hitachi replacement LCD uses positive voltage for VEE.
Have already tried taking the positive voltage from another source on the control but still no data showing on the new monitor, and can't help but wonder if it's due to the negative voltage output on the control "doing nothing" not connected and throwing the data output into an error mode.