Dell OptiPlex 755 - Manual (Page 73)

11. Reconnect the DC power cables.
12. Replace the optical drive (see Optical Drive ).
13. Connect the AC power cable to the connector.
14. 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 +12 VDC White
11 +12 VDC White
12 +3.3 VDC Orange
13 +3.3 VDC/SE Orange
14 +12 VDC* Blue
15 GND Black
16 PWR_PS_ON* Green
17 GND Black
18 GND Black
19 GND Black
20 NC NC