You would need to open the PSU and find the protection chip. Open the datasheet and see if you can find a way to disable only the voltage protection. This may involve lifting pins, adding wires or removing components.  Disabling the chip entirely would be a massively bad idea for obvious reasons. I don't recommend it either way.

The PSU has this feature for a reason; if it's tripping out now, bypassing it may result in catastrophic failure of the psu with a good chance of fire.