Hello all.

We have an iMac 27inch on our work bench minus a screen already removed by another company for a new screen to be installed.

During pre-testing the iMac powered on without any problems however on power up the machine turned on , powered off within a second or so. Pressed power button again it powers on and then off and finally failed to power on at all.

One light on logic board with AC connected as normal. Slight ticking sound from logic board (it seemed) with AC plugged in.

Swapped in a known good power supply from the same model and same results. We were then presented with a loud pop and damaged as shown in picture on the power supply.

My question is , the second good power supply is the one that was blown not the original , the original tests fine in another iMac so what would be shorted or failed on the logic board to cause a power supply to pop in this way?