I went ahead and removed the chip from the board and thats cleared the short, I'm now reading approximately 270 Ohms from the ATX connector on the 3.3v rail. Unfortunately in the process of removing the chip I've damaged the pads on the board, and the board will not start without the chip (assuming that was the only fault), so I think thats essentially rendered the board
dead at this point.

Those three components highlighted in yellow continue to measure 0.6 Ohm after removing the chip, by the way.

Hi there,

I discovered this forum through a youtuber who teaches electronic repair. I've been trying to troubleshoot my dad's old PC which is a Gigabyte GA-H61M-USB3-B3 and will not power on. I discovered a dead short on the 3.3v rail at the ATX connector so I used a bench power supply to feed 3.3v into the ATX connector and sunk about 400mA into the board (I hope that's not too much!). I used a FLIR camera to identify the problem area:

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Hi there, new user from UK.