as the title suggests I am trying to use an ATX power supply (Seasonic modular X-1050) as a stand-alone power supply. I have roughly followed guides available online, the best of which I have found to be this one on Instructables.
I have PS_ON (green) grounded to 0V (black). Once this is grounded, I switch on the PSU and the fan spins up and it briefly outputs +12V and +5V (I haven't checked other outputs) for less than 1 second. I have also tried this with PS_OK connected to +5V. The PSU then turns off until I unground PS_ON and reground it.
I have also tried the above, with the addition of a load on the +5V rail, namely two USB devices I had lying around (iPod touch and AA battery charger) and 1 laptop HDD. I estimate the load to be ~1.2A or equivalent to a ~4.2Ohm resistance.
How do I get my power supply to stay on? Do I need additionally loads on +3.3V or +12V? Thanks