I'm really getting frustrated with my new PC build. I upgraded my rig and for some reason, it won't boot when I use both 8-pin power connectors for the CPU. I even bought a new 3rd party power cable with two 8-pin connectors specifically for the CPU and switched out my PSU from a Gigabyte P750GM to a Cooler Master MWE Gold 850 V3. When I only use 0 or 1 connector from the new cable, the system powers on, but I see a red CPU error LED on the Gigabyte PSU. However, when I try to use both connectors, nothing happens. After changing the PSUs and using the 3rd party cable, the PC doesn't get any power at all, not even with the original cables from the new PSU. I'm beginning to think there might be a short circuit somewhere, possibly because I'm not using specific standoffs near the CPU power connectors, but I'm really not sure what else to check. When I eventually get this sorted, should I stick with the new PSU or is the 750 GM good enough if it works fine? I haven't built a computer from scratch in about 7 or 8 years, so any advice would be appreciated!
2 Answers
It sounds like you might have mixed up the PSU cables. Remember, even if they fit, the pinouts can be different between manufacturers. If you're using cables from the old PSU on the new one without checking the pin configuration, that can cause issues. It’s vital to use the right cables for the right PSU. I'd suggest going back to the original cables that came with the new PSU for a proper test.
Totally get your struggle, it can be frustrating! A lot of users have avoided issues by ensuring they use the PSU's original cables, as mixing can lead to powering problems or even damage. Once you figure out your boot issue, I’d say stick with the new PSU. It’s more powerful and will give you some headroom for future upgrades.
Great advice! I was in a similar situation and switching back to the PSU's cables made a world of difference. If the new PSU works fine, it's definitely worth keeping for better performance.

Exactly! Always check compatibility with PSU cables. If nothing works, it might be smart to double-check that there’s no short or grounding issue. Also, make sure all your components are seated properly.