Dell OptiPlex 755 - Manual (Page 128)

10. Reconnect the DC power cables to the power supply.
11. Connect the AC power cable to the AC power connector.
12. Replace the computer cover (see Replacing the Computer Cover ).
DC Power Connectors
DC Power Connector P1
Pin Number Signal name 18-AWG Wire
1 +3.3 VDC Orange
2 +3.3 VDC Orange
3 GND Black
4 +5 VDC Red
5 GND Black
6 +5 VDC Red
7 GND Black
8 PS_PWRGOOD Gray
9 P5AUX Purple
10 V_12P0_DIG White
11 V_12P0_DIG White
12 +3.3 VDC Orange
13 +3.3VDC/SE* Orange
14 -12 VDC Blue
15 GND Black
16 PWR_PS_ON Green
17 GND Black
18 GND Black