Rebuilt pc now wont boot.

soundb0y

soundb0y

soundb0y

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Joined
19 Mar 2009
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Hereford
Hi guys wandering if anyone can help.

Last week my pc died a death. I assumed this was the fault of the psu so ordered another and the computer still wouldnt post but had power. So today a new mobo arrived (gb udr-3).

I have just built the machine but for the life of me cant get it to boot, it keeps powering on, spinning the fans then stopping. Then on its own it will try to boot again and keeps doing this?

Any idea what the problem could be? I cant think what I can have missed. None of the case fans or cpu fan has been connected yet but that shouldnt stop it should it?


cheers in advance
 
Couple of things, is the ram in the correct slots, done this on my build, usually need to be in the 2nd, 4th and sixth slots from the CPU.

All power connections ok including the 8 pin for cpu power.
Try a CMOS reset.
 
Trying with just one stick of ram and its doing the same. Also have done a cmos reset by removing the battery for 20 mins and that's done nothing either.
 
Hmm removing the cpu power the machine powers on and the gpu spins up and it doesn't reset. Put the cable back in and it keeps powering on and off.

Any ideas, im at my wits end and going mad if I cant fix it after a new mobo AND PSU
 
do you have another cpu you could test as if you have a new mobo and a new psu and it's still doing it there's only a few things that could be wrong left
 
try the ram in different colour sockets, had the same with my i5 wouldnt boot and spent ages trying to work it out. moved teh ram and it fired up first time :)
 
I don't have another cpu to test unfortunately. The new motherboard is the gigabyte x58 ud3. My old one is an evga x58 sli board. It is a B grade so maybe this one is also faulty as it is doing different things.

I have tried one stick of RAM in evey slot.

I have tried both my 4890s in both slots.

The old psu is a bequiet! darkpower 850w. The new psu is https://www.overclockers.co.uk/showproduct.php?prodid=CA-046-OC

I have reset the CMOS
 
I know this is a daft question but have you tried to power up your kit outside of the case?

I had a similar problem a few months ago, and after replacing all my kit, I found out it was my case causing the problem ... there was a short somewhere, after I got a new case, all was fine, but it meant I was stuck with older tech that cost more than the newer tech does.
 
No I haven't what sort of surface can I have it on if I was to do this?

I don't think it is the case though as I am getting a different issue with the different motherboards. With the original EVGA board everything is powering up and staying powered on but it will not post. With the new Gigabyte board it powers up for a second then powers down and does this on an infinite loop.

However when the cpu power is pulled the board will act the same as the evga.

So confused. Have spent so much on replacement bits and seem to be getting nowhere!
 
The new PSU is a 4 X 12v rail at 18A each, therefore the maximum watts is 216w per rail. Is this enough for your graphics card(s)? Radeon 4890 can use 210-220w at idle. My first thought is that one or more rails is overloaded. Have you tried just one GPU, I suppose so? If you have a smaller capability GPU, (I use a PCI radeon 7000 for testing), use that.
This is suggested by the fact that removing the 12V CPU power seems to improve things. Another thing to try is a molex to PCIe adaptor to see if you can balance the power across the rails a bit.

The four available rails are divided like this: courtesy of hardwaresecrets

+12V1 (yellow wire with blue stripe): ATX12V connector labeled as “CPU1”
+12V2 (yellow wire with white stripe): ATX12V connector labeled as “CPU2”
+12V3 (solid yellow wire): Main motherboard cable and all peripheral connectors
+12V4 (yellow wire with black stripe): Video card auxiliary power connectors (Both graphics card connectors here)

EDIT looking at the above, it appears the PSU is not man enough for the requirements The previous one had 2 x 18A and 2 x 30A rails. Combining the two graphics connectors on one rail appears a bad idea and it seems marginal for just one card at idle. A PSU with a large single rail would perform better IMHO.

andy.
 
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