Hey all I am using an old Dell Precision R5400 which has the 750w hot swap-able power supply. Problem being, since its a dell, the ATX pin layout is different than that of a normal, standard ATX 2.0 power supply pin out.
What I found to be the Standard ATX 2.0 pinout:
I have taken a volt meter to the R5400's ATX pinout and this is what I come up with:
 Ground  Ground  +5v  +5v  +5v  +5v  +12v  +3.3vsb  -12v  Ground [ 6] Ground  Ground  +3.3vsb  +12v [ 8] +3.3v  +3.3vsb  Ground  +12v  +3.3v  +3.3v  +3.3v  +3.3v  +3.3v  +3.3vsb
Thankfully my motherboard's manual shows the pinout of it's ATX power supply connector:
So some questions are still wondering inside my head:
1) What voltage should the PSON# be?
2) What voltage should the Power OK be?
3) As you see, I do not have access to a +5Vsb from the R5400 PSU. Can I just use a normal 5vdc for that (or somehow get 3.3vsb that I do have to work with it)?
Currently this is my pin-out for my new connector from the R5400 connector to the motherboard:
So do you see anything wrong with the above? Just making sure as I do not want to fry a $500+ server motherboard over one wrong pin.
Ref Your questions, according to ATX standard.
PS ON is not output of power supply. It is input. If You want PSU to start You need to connect it to ground. Mistake in here "fries" the PSU.
In the "classic" specification "Power Good" should have +5V when PSU is confident it provides proper voltage on all outputs. When this output is below or above, the motherboard and OS should quickly take action to flag the PSU is not working properly. Initially it was used for MB to wait with the boot until PG stabilized at +5V.
The ATX standard states that the +5V SB is 5V in standby mode, so when PSU is connected to power but not "on" started yet. Lets say it supplies the "blinking led" when PC is in standby (making this an awful shortcut as it powers up a lot of other devices to keep memory state).
Disclaimer: basing on the measurements it seems You have mis-ordered the pinout numbers on the male-female plug (so, please cross-check). Not sure if Dell did not implement own "interpretation" of ATX standard, so the information provided may not be accurate.
The only recommended way is to replace the PSU for a know good one especially for a server.
The information provided should be used for DIY activities, not server HW troubleshooting. ATX PSUs are great for LED lighting, phone charging, home automation and that seems to be the case for the mentioned PSU.