Dell OptiPlex GX520 - Manual (Page 103)

DC Power Connector P2
DC Power Connectors P3 and P5
DC Power Connector P4
DC Power Connector P7
19 GND Black
20 NC N/C
21 VCC (+5 V) Red
22 VCC (+5 V) Red
23 VCC (+5 V) Red
24 GND Black
*Use 22-AWG wire instead of 18-AWG wire.
Pin Number Signal Name 18-AWG Wire
1 COM Black
2 COM Black
3 +12 VDC Yellow
4 +12 VDC Yellow
Pin Number Signal name 18-AWG Wire
1 +3.3 VDC Orange
2 COM Black
3 +5 VDC Red
4 COM Black
5 +12 VDC Yellow
Pin Number Signal name 18-AWG Wire
1 N/C
2 COM Black
3 COM Black
4 + 3.3 VDC Orange
5 +5 VDC Red
6 +12 VDC Yellow