Disclaimer: WARNING! Modifying electrics is dangerous! Do so at your own risk. I'm an idiot! So doing the things I do is not safe.

PLEASE BE SAFE!

This is how I modified a Hipro HP-W500FF3 Server Power Supply for use on my printer. This would also work for the Hipro HP-R650FF3 PS.

Hipro HP-W500FF3 500W Server Power Supply
12v @ 41 Amps
5v @ 2 Amps

This has a slot style connection. With the Hipro label up, and facing the fan the top of the connector left to right under the fan.

^ ^ ^ ^ ^ ^ |----------| |----------|
1 2 3 4 5 6 Gnd. 12V

3 Ps_On
4 Ps_Kill
6 5vsb

Bottom side of the blade two larger pads are Gnd and 12v again

Remove the 5 screws shown
And open the case to make it easier to solder wires.
Pull the case up, and connect wires on the correct pads.

To turn on the power supply connect both Ps_On and Ps_Kill to Gnd.

You could connect a on/off switch between PS_On and Gnd, and a
Emergency Kill button between PS_Kill and Gnd.

I've made a cover to attach to a 20x40 extrusion for my printer.
I included the Openscad files so you can edit it for what you need.

I added a case that fully encloses the power supply.

Disclaimer: WARNING! Modifying electrics is dangerous! Do so at your own risk. I'm an idiot! So doing the things I do is not safe.

PLEASE BE SAFE!
This has a slot style connection. With the Hipro label up, and facing the fan the top of the connector left to right under the fan.

^ ^ ^ ^ ^ ^ |----------| |----------|
1 2 3 4 5 6 Gnd. 12V

3 Ps_On
4 Ps_Kill
6 5vsb

Bottom side of the blade two larger pads are Gnd and 12v again

Remove the 5 screws shown
And open the case to make it easier to solder wires.
Pull the case up, and connect wires on the correct pads.

To turn on the power supply connect both Ps_On and Ps_Kill to Gnd.

You could connect a on/off switch between PS_On and Gnd, and a
Emergency Kill button between PS_Kill and Gnd.

I've made a cover to attach to a 20x40 extrusion for my printer.
I included the Openscad files so you can edit it for what you need.