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New Build: Immediately powering off after being switched on

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February 3, 2012 5:02:55 AM

I recently bought a new set of hardware (except PSU, which is from an old rig that had not a single issue in its lifetime), but every time I turn the computer on the CPU fan twitches, the PSU clicks, and the rig powers down.

The motherboard power light LED is on, so the board is getting power, but whenever I power the rig itself the CPU LED flashes for a split second, the CPU fan attempts to spin for a split second, and then the PSU clicks and the rig powers down. The motherboard LED stays on, but using the power button has no subsequent effect unless I turn the entire unit off at the plug.

I have spent the past few hours reading over various websites and forums for assistance but nothing I have tried appears to work:

- I have tried using a different (more powerful) PSU. No effect.
- I have changed the standoff positions and even had the motherboard resting on a non-conductive material (just in case there was a short in the case).
- I have tried with various sticks of RAM in the various motherboard slots.
- I have re-pasted the CPU in case it wasn't connected property to the heatsink.
- I have checked every connection to ensure there aren't any broken or disconnected pins (including CPU and all motherboard connections).
- I have run the system on the bare minimum (just a CPU and its fan and a single stick of RAM) in case the PSU wasn't providing enough power.
- I have shorted the power-up manually in case it was an issue with the power button.
- CMOS reset via jumper.

The whole computer was put together with utmost care, so I highly doubt I've damaged a component myself. Much of the advice online suggests a dead motherboard but I really don't want to have to provide proof and send it back. Does anybody have a suggestion that might aid in troubleshooting?

Rig specs:

PSU: 750w (24A on 12V1 and 12V2, 30A on 3.3V, 33A on 5V).
Motherboard: Asus M5A97 PRO 970 Socket AM3+ 8 Channel HD Audio ATX
CPU: AMD FX-4 4100 Black Edition 4 Core 3.6Ghz Socket AM3+ 8MB L3 Cache
RAM: Corsair XMS3 DDR3 1333MHz 4x4GB
a b B Homebuilt system
a b V Motherboard
February 3, 2012 5:27:45 AM

First, do you have an 8 pin 12v CPU plug from the power supply plugged into the appropriate socket next to the CPU? Your initial PSU sounds like an older revision that would only have a 4pin CPU 12v connector. This will not work on newer multicore CPUs.

Secondly, even though your motherboard is AM3+, it's BIOS may not be updated to recognize the new CPU. In the past, most machines would still boot and run with a misidentified CPU. You could then update the BIOS and be on your merry way. However, this is not the case with the new FX CPUs.

You would need to check the revision number stamped on your motherboard to try and determine which BIOS revision it might have and compare it to the one on the ASUS web site list of approved CPUs.

Unfortunately, the only ways to fix the CPU bug is to either exchange the motherboard for the latest revision, if even possible, or buy, borrow, or steal an older CPU that the board will boot. In the case of buy, the ~$35 Sempron 145 would suffice.
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February 3, 2012 7:08:33 AM

Further to my initial post (and before I saw tlmck's post), I tried using an AM3 CPU and it made no difference, indeed I couldn't even get the CPU LED to flash.

Of all the things in the world, I changed the socket my PSU's fan was plugged into, and viola, the power remained on using the AM3 (the case fans were spinning, as was the CPU fan), and the board ran a number of checks (via LEDs lighting up for RAM, boot device, and VGA). When reverting back to the AM3+ (recent purchase) the power remained on but the board did not run these checks, so I'm very much assuming that tlmck's idea about the board not recognising the CPU is bang on the money.

I haven't been able to see on-screen what information the board throws up (having to rely entirely on the LED system the board employs), as my PSU's 12v 4-pin (which seems to be working) is too short to reach unless there's a card removed, and the board itself has no on-board graphics capabilities that I can see. I'm on my way out to pick up an extension cable (as soon as I finish writing this), and then I'll be able to diagnose a little better what other problems there might be.
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a b B Homebuilt system
a b V Motherboard
February 3, 2012 7:39:33 AM

As I have a bottom mount PSU, I wound up having to run the 8 pin 12v cable under the back of the video card to the 8 pin socket. Most video cards will have a notch cut out between the PCIe card edge and the steel back plate that mounts to the case.

Even though it appears to work, you are still going to need a PSU with an 8 pin EPS 12v motherboard connector. If you had one of the dual core CPUs, it might work with the 4 pin. As far as I know, there is no 4 to 8 pin adapter.
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February 3, 2012 7:45:19 AM

I've tried running it under the card, still won't reach. Maybe I'll just pick up a new PSU, all of the new lighting/fans and both new graphics cards I'll get in the near future will probably need more power than a two year old 750w can churn out anyway.

I'll update shortly when I fix up the new cables (I haven't left to buy them yet) and see what info I can get via a monitor.
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a b B Homebuilt system
a b V Motherboard
February 3, 2012 8:15:00 AM

I would recommend at least an 80 plus certified power supply from Antec, Seasonic, Corsair, Silverstone, or XFX. Wattage would main depend on which graphics card you have, but a 650w will run any high end single card out there. If you had intentions of going dual card, then a 750 watt bronze certified would be better. These days with the new certified units, it is no sin to get more watts than you need as they are efficient at all load levels.
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February 3, 2012 8:52:12 AM

Status update: I've managed to get everything working, though I have no idea what I did to make it do so. I'm currently using the AM3 CPU and going through Windows' repair sequence (actually as I typed this it finished the repair and is rebooting, not sure if it will work or not -- it didn't).

Going to update the BIOS to accept AM3+, then I'll see if I can get that one working too. With any luck I'll have it working in the next couple of hours.

Thanks for all of your help tlmck, it's been very much appreciated.
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