I think your PSU automatically switches between AC voltages. The button you're referring to is just an on/off switch, not an AC voltage selector switch.
In any case, you may want to jump start the PSU with a paperclip and see if it remains on for longer than 10s. And if it indeed does and doesn't make any strange noises then there might be a problem with your mobo or other components.
You can also check its DC voltages with a multimeter, which is much simpler than it sounds. Let me know if you need any help in this regard.
Is you PSU modular? The CPU and PCIe cables may be swapped the wrong way around. I believe the pinout is different and would cause the protection circuit to trip.
FrankOcean_ reacted to Man in HELP! PC starts up w/o the ATX_12V.
