Dell OptiPlex 755 User Manual page 222

Pin
Number
7
8
9
10
11
12
13
(optional)
14
15
16
17
18
19
20
21
22
222
Power Supply
Signal Name 18-
AWG
Wire
GND Black
PS_PWRGOOD* Gray
P5AUX Purple
V_12P0_DIG Yellow
V_12P0_DIG Yellow
+3.3 V Orange
+3.3V Orange
-12 V* Blue
GND Black
PWR_PS_ON Green
GND Black
GND Black
GND Black
NC NC
VCC (+5V) Red
VCC (+5V) Red