This is a three year old pc with no past issues. Currently I've got just the motherboard, cpu and psu out on the desk. It powers up for half a second, then off for two seconds and so on until I turn off the power. Last week windows display artifacted a bit and then bluescreened. Memory diagnostic came back clean and it continued to work for a few days. Then on a startup no display output. Unfortunately I don't have a system speaker so I've no idea if anything went on there. I stripped out the gpu and went to cpu video output with no luck. Then messed around with the ram and got it workig after removing from one of the slots. Bad RAM slot then. Put it back together and it worked fine for an evening before the half second boot loop issue. I don't have the spare parts to do component testing. Any advice aside s from new build?
First off, specifications of the machine would be helpful in finding a resolution to your problem. Secondly, As fiddling with the ram got it working again, im assuming its probably just a dirty contact on the ram itself, which you can clean by rubbing both sides of the ram's gold contacts with a soft pencil eraser or a cotton bud and some isopropyl alcohol. (if you have neither of these things try taking the ram out and inserting it back in the slot a few times)
I5 3550 H67ma-e35 Antec truepower 550 2x4gb 280x If its the RAM why the bootloop when it is solely motherboard and cpu?
Is the 4 pin ATX12V connector seated correctly? Also, try it with just one stick of RAM in for ease of ruling stuff out. Running no RAM at all will just cause more issues than it solves.
Unfortunately no amount of swapping the ram around and checking the 24 and 4 pins are seated has caused any difference. Half a second is all it ever manages
BIOS reset? Failing that, I would say it's time that additional hardware is needed for trial and error testing.
I've taken the battery out for half an hour with no luck. A quick phone around today and no one has the old motherboard needed for testing beyond the power supply. Is it likely that is good given the lead up memory problems?
I recently had the same problem with my S775 set up. No memory issues, but showing some instability generally. I underclocked it a bit and it seemed fine for a day or two. Then it went into the loop - power LED and the LED's on the motherboard lit up for half a second, then it went into a reboot cycle and repeated until powered off. After dismantling the system I noticed some areas around the CPU pins were deformed/melted. So for me it was the motherboard (CPU is in another board now and working fine), and I would point the finger at that for your issue too.
In conclusion it was the motherboard/cpu. The pair will probably go on the marketplace at some point. Chances are the CPU is fine but I don't have the time to find a 1155 board second hand. No obvious pin burn marks like yours blacker but it sound very similar.
Check the CPU ATX12v again (and the 24pin ATX connector while you're at it). My PC had exactly the same symptoms last week and despite assembling & disassembling it many times as I was trying to resolve the issue, and checking the connections each time, the problem turned out to be a badly seated power connector. I've never had this problem before but it seems the sockets on modern motherboards aren't as failsafe as they used to be. Honestly, for a long time I just couldn't fathom what the hell was going on at all and it nearly sent me completely hatstand. So, even though the connectors may look fully inserted, check them again and give them a firm press an gentle wiggle to make sure.
