Xbox ONE S turns on, Light goes dim and then the power just drops off

Question

Hello, Recently I have decided that I want to repair my Xbox One S which about a year ago all of a sudden decided that it was going to play up. It turns on but then the light goes dim and then the power goes off. I have; checked the voltages of the moffets along the 12v rail near the GPU. I have also checked the majority of the Resistors around the motherboard and from what I can see there is no physical damage. I have replaced the PSU and that did not do anything too fix the issue. I Have just changed the thermal paste along the heat sync. I have also checked too see if the motherboard will boot without the Hard drive and also the Disc Drive but still the issue persists. I have also tried to blow the fan with a hairdryer on cold to see if it will stay cool and then turn it on but the issue still occurs. Does anyone have any other solutions/things that I should try that I haven't listed above; Or have any idea on maybe what my issue might be.