Reuse PSU for other devices

I want to reuse a 21.5 2009 imac PSU to power other devices.

I can get power on the 12V and 3.8V standby pins, but with no logic board I can't get the power to turn on for the other pins. I also want to get power on the SATA cable and the display inverter cable from the original imac logic board power cable harness.

Is there a way to trick the PSU that the power button has been pressed?