E0028
Servo error: Drive unit voltage down.
This error occurs when the +15V dc drops to +13V dc or less on the Servo detecting circuit on the UM843-1 or 2 PCB in the Servo Drive Amp (Servo Amp. Unit) or when the 100 V ac drops to less than 80 v ac for 20MSEC or more.
(1) Check if primary supply voltage drops below normal value (±10%).
(2) Check if output voltage of switching regulator in the Servo Amp. unit is +15 v dc ±0.5 v dc (AR 10, 11 or 13 controllers).
(3) Check 18 v ac on Servo Amp. Unit from T13 in Power supply unit (AR 50, 51, 52 or 54 controller).
(3) Check connectors on the Drive Amp. Unit (Servo Amp. Unit).