Brand new parts, PC still broken - please help

Hi again. I'm afraid that my PC still isn't working, so I have come here in the hope that someone at Scan can try to sort out the problem. Let me just give you a quick rundown.

I switched on my PC back in November last year, and I heard the PC spin up, then spin down and it kept repeating the pattern. So I pulled it out of the case, and started removing components in the hope that I could pin it down to something specific. Eventually I got down to just the motherboard (GA-P35-DQ6), the power supply (Hiper Type-R 580W) and the CPU, an Intel e6750. I discovered that the CPU fan was failing to kick in, and the computer was failing to do anything, with the power supply just restarting itself before anything could happen. However, if I unplugged the 4-pin power cable, leaving only the 20-pin power cable attached to the motherboard, the power supply would not try to restart itself - obviously the PC wouldn't work without the 4-pin power cable attached though (according to the manual that provides power primarily to the CPU). So I decided that it was probably the motherboard, and returned that to scan. The RMA was rejected on 05/11/08, because the motherboard was tested and found to have no fault.

I spoke to someone at Scan, a bit confused, and they suggested that I should return the PSU so that the problem could be isolated, but as I'd bought it from OCUK I had to send it back to Hiper. They tested it, and concluded that it was indeed faulty, and sent me a replacement. I paid to have the Gigabyte board returned to me, and then plugged in the replacement PSU, a refurb, and the problem was the same. I then talked to a guy I know, who suggested that it was probably still the PSU, and provided me with another one to test it with - again, the results were the same. I went back to Scan, and told the people over the phone that the only thing left was the CPU - with the CPU out of the socket, the PSU didn't restart. They suggested going through Intel to replace it, and after a real saga in which I discovered it was virtually impossible for me to conduct the tests Intel wanted me to do, I went back through Scan again, and returned the e6750 to you at New Year's.

You agreed that the CPU was faulty on 05/01/09, but as I mentioned in a previous post there were real issues over getting a replacement to me, so on 20/01/09 I agreed to receive a cash alternative. Then I got some advice on Hexus, and purchased a new Q9550, Corsair HX620 and Corsair XMS2 PC2-8500 RAM to drop into my motherboard. I received that today from Scan, and set it all up just now. However, it's still doing exactly the same thing as before. So in summary I've replicated the problem with two CPUs, four power supplies, and two sets of RAM (and without any RAM at all).

My further testing today has shown that if I plug the fan directly into the power supply to keep the Thermalright Ultra-120 Extreme cool, the fan spins at full speed but the problem repeats itself (besides, the PSU is restarting far too quickly for the Ultra-120 to even get warm). If I put in the graphics card, no output to the monitor is made before the PSU reboots, although it does spin up the fan. If I unplug the four pin power plug from the motherboard, the PSU does not reboot, as before, but the graphics card won't spin up so I can't get anything on the monitor.

If I've not tested something obvious, then please let me know, but at the moment I'm just really at my wits end. I've had so many parts sent here, there and everywhere, and determined faulty/non-faulty, and replaced quite a few, and I'm just so lost it's unreal. I just want my PC back :(

Just rang up and spoke to someone in the RMA department who is going to issue an RMA number for the motherboard so that it can be returned and re-tested. I'm assuming that if it starts working again I'll have to send back my power supply and CPU until you can tie it down to something in particular. If you could keep me posted on what the testing turns up then I'd appreciate it.

Thanks

check the emergency shutdown isnt enabled on no detection of cpu fan or cpu fan under a certain limit (might be hard to do if getting no boot!) so try reset cmos as well.

If no joy with that, you can try plugging a normal 3 pin fan into the cpu fan header to test that as well, so long as the fan spins fast, see what happens but dont leave it like that for any length of time, jsut use it as a test ot check for the possible problem i outlined above.

Is this just not a bios protection setting for temperatures?

If the temp in the lower/higher switch offs are set wrong, nothing will power up.

Just a thought.

also check that you havent got a short on the motherboard from a stand-off or something, might be an idea to try it with out the front panel switches plugged in, using a screwdriver to sort the pins on the power header (i've had similar issue before where it was a faulty reset switch on the case)

Or even build outside the case first.

I've tried CMOS resets, and all tests have been done without a case, and as such I've been using a screwdriver to turn it on, so I'm still not sure. Also - the fan I've been using so far is a 3-pin anyway, and works perfectly when plugged direct into the PSU... the boxed Intel cooler did exactly the same thing when plugged into the CPU Fan pins.

Anyway, I got an email from Wesley earlier today confirming that Scan will pick up the Corsair PSU, motherboard, Q9550 and Corsair RAM. According to what the woman I spoke to told me, they should run some tests to figure out which part(s) is/are causing the problem and hopefully sort this mess out. Fingers crossed, that will be the end of it :/

I would really suggest you take the PC to someone with a PC you can test ALL of your components on.

I had a problem with the PC, and it came down to PSU and RAM, I thought it was the PSU, and it turned out to be RAM. When you are 100% then you RMA something, otherwise you're just wasting your own time imo.

Well, the new verdict is that the motherboard is indeed faulty, and the PSU, CPU and RAM is all okay, and they still have P35-DQ6's in stock so I should get a replacement along with my PSU, CPU and RAM.

However, even though I've had the same problem ever since I originally returned the mobo they aren't going to refund the non-faulty item charge I had to pay in November. Apparnetly they only refund those charges when it's over a 28-day period... it's a bit annoying after I've spent so long trying to sort it out and it was the motherboard all along, but there you go.