Back in the autumn I ordered a new PC from 3XS. After some delays it got delivered, but had RAM problems. These were fixed and the machine was mostly OK. It still suffered from some reliability problems, however, due to the sometimes it would fail to power-up properly (usually it would fail to establish the overclock, sometimes fail to boot). As this fitted an existing pattern of problems that had been observed with the PSU I had originally specified it was agreed that the original PSU would be swapped out and replaced with one of a similar spec of a different brand.

This finally happened yesterday. I was not able to be there when the engineer did the swap out, but he left the machine for me to do a power-up test when I got home. Sadly, the machine refused to power up. All that happens is that the CPU fan and one of the case fans briefly whirls into life and then stops. Pressing the power button again has no effect. If I switch off the PSU power button, then switch it on again, I can get the CPU and case fan to whirl into life briefly again, but no further.

I've tried clearing the CMOS RAM, I've tried removing some of the RAM (eventually just leaving one stick in), but no improvement. The various cables look seated firmly (not tried unplugging and replugging). I've tried unplugging a case fan lead, but again to no avail.

Help?

Motherboard: Gigabyte GA-X58A-UD3R
CPU: Core i7 980X
Memory: 6x2Gb DDR3
Graphics XFX 6970
PSU XFX P1-850B-NLG9 Black Edition 850W