Compaq Deskpro EP and EN Power Supply

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This pinout is as standard ATX v.1 Except for PWR_OK and PS_ON.

Image:connector_atx20m.png 20 pin MOLEX 39-01-2200 connector at the PSU cable.

Pin Name Description
11 +3.3V
1 +3.3V +3.3V/RS in Deskpro EN
12 COM
2 +5V
13 COM
3 +5V
14 COM Aux COM in Deskpro EN
4 Fan OFF may be +3.3VSB in some server PSU
15 +5VSB
5 +12V
16 +3.3V
6 -12V
17 COM
18 COM
8 COM RTN/RS in Deskpro EN
19 COM
9 -5V
20 +5V
10 +5V


  • A Compaq SP750 Server Power supply (Such as PS 7431-1) uses the same pinout as an ATX power supply, except that PS_ON is inverted, and PWR_OK is replaced with 3.3VSB. The wire colors are also different.
  • To use this supply with a normal ATX motherboard:
    • cut PWR_OK and tie the motherboard side of the wire to 5v
    • leave the power supply side of the wire unconnected
    • use an inverter such as a 4096 or 7404 to fix the PS_ON signal
    • tie the chip’s Vcc to 5VSB and GND to GND
    • cut PS_ON, and hook the motherboard side to an inverter’s input, and the PSU side to the inverter’s output
    • tie all remaining pins to ground
  • An Inverted PS_ON signal is also common in G3 iMacs.


Category:Power Supply Connectors


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