Replacing power supply with ATX PSU?

Hello everyone,

The PSU of our 2006 Intel iMac failed, replacing it with an original Apple PSU would be a tad expensive. I have a couple of questions regarding a replacement with an ATX PSU.

Is there anybody who has experience with replacing the standard PSU with an ATX one?

Does anybody know what voltage each pin from the DC-connector needs? GND, 12V and 24V, but which pin is which?

Would it be safe to connect the iMac ground to the -12V on the ATX PSU, the 12V to the 24V and the 0V to the 12V pins?

Thanks!