Power supply making weird noise when connected to power and mobo

I just bought this power supply today (CX 500), and I did a test on the power supply before hand (shorting green with a ground wire), the power supply did turn on without trouble, and no noise.

The problem is, as soon as I connect the 24 pin ATX power cord onto the mobo, and turn the switch on the back of power supply to ON, it starts making a weird high pitch noise. (Note: the computer is not started)


I CAN start the computer, in fact, I actually successfully installed my OS onto the computer (I thought it was just PSU not warmed up enough), but as soon as I shut down the computer, the noise returns.

I can stop the noise from happening, by either:
(1) cuts off the power to power supply via the switch, or the cord. And after a while the noise will die down.
or
(2) remove the 24 pin ATX power cord from the mobo, this will stops the noise.


I am using ASRock z68 Pro3-M, and I have yet to get a different PSU.

Now, has anyone experienced this before? IS the PSU bad, or could it possibly be my mobo?