Need help with converting a ML370 G5 PSU backplane to ATX

[Average nerd]

I have recently aquired a HP ProLiant ML370 G5, and since it came with dual redundant 1000W PSUs I want to convert the Machine into a more modern PC. But I have come to the conclusion that I cannot figure out how to get the backplane to turn on, since the PS-ON signal is likely hidden away in the 25-pin header that connects to the motherboard throug some thin wires. It also carries signals for fan control, because the servers fans plug straight into the backplane. I have spent hours of trial and error, but only the auxiliary rails worked.
Any help would be greatly appreciated.

[jaslion]

Track the power button cable and then see which wires are which?

[Average nerd]

 

4 minutes ago, jaslion said:

Track the power button cable and then see which wires are which?

Power button is integrated into the system insights display and disappears in its cable harness. I tried connecting only the 25-Pin header to the mb and pushing the power button, nothing happened.

[jaslion]

1 minute ago, Average nerd said:

 

Power button is integrated into the system insights display and disappears in its cable harness. I tried connecting only the 25-Pin header to the mb and pushing the power button, nothing happened.

So basically the 25pin is carrying the power button signal somewhere. I'd say get some small breadboard wires and try finding a ground and a power signal with a multimeter when you press the power button.

[Average nerd]

1 minute ago, jaslion said:

So basically the 25pin is carrying the power button signal somewhere. I'd say get some small breadboard wires and try finding a ground and a power signal with a multimeter when you press the power button.

The Power button is connected directly to the motherboard via the system insights display cable, so finding the signal migt be difficult but i will try that when i get home.

[jaslion]

3 minutes ago, Average nerd said:

The Power button is connected directly to the motherboard via the system insights display cable, so finding the signal migt be difficult but i will try that when i get home.

I mean find it in the 25pin cable. You dont even need power just a complete circuit. Going to be a lot of trying as you'll try 1 pin negative and then 24 pins for positive over and over. Whilst holding the power button down

[Average nerd]

14 minutes ago, jaslion said:

I mean find it in the 25pin cable. You dont even need power just a complete circuit. Going to be a lot of trying as you'll try 1 pin negative and then 24 pins for positive over and over. Whilst holding the power button down

Ah that makes more sense, thanks!

[Average nerd]

I figured it out! Trough some continuity testing i found out that several wires of the 25 pin cable were connected to the same pin on the power button, so i tried setting a bridge between two of those pins (see attached image), which caused the backplane to start, for now I have only tried starting with one PSU connected.

[Average nerd]

3 minutes ago, Average nerd said:

I figured it out! Trough some continuity testing i found out that several wires of the 25 pin cable were connected to the same pin on the power button, so i tried setting a bridge between two of those pins (see attached image), which caused the backplane to start, for now I have only tried starting with one PSU connected.

 

Redundancy seems to work as well, the fault LED is at least not lighting up and the correct voltages are being outputted.

[Average nerd]

So this should be all the pins needed from the 25-Pin header for standard ATX, the blue wire is PS_ON and just needs to be shorted to ground to turn the unit on, as expected, the white wire is should be PWR_GOOD, since it is the only pin carrying a 5V signal when the PSU turns on. The Rest of the pins are most likely for fan control, and for the system insights display. The power cables are all labeled with their respective voltages, the colourcoding is not entirely standard though.

@jaslion, many many thanks for your help, i really apprechiate it!