Hi all,

As the subject line (plea for help!) says, my brand new Corsair RM550x power supply will not power up when there are any peripherals connected to it. Not even just one! However, when it is connected to just the ATX and CPU on the motherboard, I get a blue power light and the fans all start spinning. As soon as I connect even one peripheral, no matter which one, it will not power up.

This is for an HTPC, so I can't imagine 550W is not enough for three hard drives, a blu-ray player, and a sata controller.

I am wondering, could this be a motherboard issue? Would the computer power up at all if the motherboard were damaged? The reason I ask is because I am replacing a PSU that died a few days ago. I heard a loud POP, and the whole unit shut down. I did the paper clip test on the PSU and yep, it was dead. I then tried a EVGA SuperNOVA 750 B1 80+ BRONZE PSU, but it died as soon as I powered it up (all peripherals connected), with a wisp of smoke drifting out of the PSU itself. Thinking, and hoping, that I just got a faulty PSU, I purchased the Corsair. So, this is my third PSU. It has not blown up, but it will only power up when there are no peripherals connected.

I have looked at both sides of the motherboard and it looks fine. No black marks or melted solder anywhere that could be causing a short, as far as I can tell anyway.

I'm at my wit's end and could sure use some expert advice.

Thank you!

1 Year
Discussion Span
Last Post by ssa-ed

Sounds like a short circuit on the mobo to me. Some of those are hard to find if you aren't an experienced computer tech or electrical engineer.


What kind of mobo and CPU do you have?
If I had your system in my shop, I'd unplug everything and remove the CPU. You may have to remove the mobo (and PSU) from the case and even if not needed, it's always best to get the case out of the way. This also allows you to inspect the underside of your mobo. While out of the case, re-connect the PSU and re-start (short the power posts on the mobo MOMENTARYILY). If you can't get the BIOS to report a "no CPU" problem, you have a dead mobo. if the BIOS reports in, you mobo is not the problem. Warning: Do not re-install the CPU and heat sink without thermal paste!

Edited by ssa-ed

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