New i5 system wont boot


Just upgraded my PC using

Gigabyte GA-P55A-UD3R P55
Intel Core i5 750 Processor LGA1156 2.66GHz 8MB Cache CPU
G Skill 4G(2x2G) DDR3 1600Mhz PC12800

Will not boot!!! No beeps, in fact runs for about 1s to 2s then resets and goes again. Sounds for all money like a short resetting the PSU.

Gigabyte uses this phasing LED system and according to the manual the more LEDs illuminated the higher the CPU loading. All 6 are illuminated for that initial period before it resets.

I replaced 430W PSU with 600W OCZ PSU and no difference.

Have done everything suggested and I'm now bread-boarding it with nothing installed apart from the CPU.

I guess I'd like some advice on whether to try another mobo or CPU first. I read somewhere that you should always try the mobo then ram then CPU when diagnosing by replacement.

Any thoughts?

Given that I'm a home builder (fairly experienced) I'm now getting a little nervous that I may not get a refund so I'd like to nail it first time.

Any help would be much appreciated.

2 answers Last reply
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  1. You have worked through our standard checklist and troubleshooting thread:

    I mean work through, not just read over it.

    Breadboard - that isolates any kind of case problem.

    Breadboard with just motherboard, CPU & HSF, case speaker, and PSU.
    You do have a case speaker installed, right? If not, you really, really need one. If you case or motherboard didn't come with a system speaker you can buy one here:

    You can turn on the PC by momentarily shorting the two pins that the case power switch goes to.

    You should hear a series of long, single beeps indicating memory problems.
    Silence indicates a problem with (in most likely order) the PSU, motherboard, or CPU.

    The problem with OCZ PSU's is that, depending on the model, they range from "pretty good" downward to two steps above junk. That's why I do not recommend OCZ PSU's. (I'm old. I never can remember which are the good ones.)

    So, the best bet is to replace the PSU with a known good one of similar power capacity. Brand new, out of the box, untested does not count as a known good PSU.

    Next best thing is to get (or borrow) a digital multimeter and check the PSU.

    Yellow wires should be 12 volts. Red wires: +5 volts, orange wires: +3.3 volts, blue wire : -12 volts, violet wire: 5 volts always on. The gray wire is really important. It should go from 0 to +5 volts when you turn the PSU on with the case switch. CPU needs this signal to boot.

    You can turn on the PSU by completely disconnecting the PSU and using a paperclip or jumper wire to short the green wire to one of the neighboring black wires.

    This checks the PSU under no load conditions, so it is not completely reliable. But if it can not pass this, it is dead. Then repeat the checks with the PSU plugged into the computer to put a load on the PSU.
  2. jsc,

    Thanks for your reply.

    Yes yes and yes. I'm not one of these young kids who think they've done it by reading about it.

    I had done all of that prior to finding the advice you refer to on Tom's Hardware

    It is a brand new out of the box PSU. I have checked it with a DMM unloaded and loaded. Power on (grey) goes to 5V then the whole thing resets itself. Exactly as it did with the old 430W PSU so I've blown my money on that one.

    I have done exactly what you suggest here almost to the letter. I have a speaker from an old PC and verified it is ok by plugging it into my running PC first.

    The only sound it makes on this i5 is 2 "pops". I initially thought it was a relay dropping in and out. I've looked at the Gigabyte site for the award bios post beeps and thought it could have been the cmos so I removed the battery for a few minutes.

    I've also reset the bios to factory.

    I have just never been in a position where I have built a PC and not have it work so I wanted advice on what to try first given I've outlayed the money for a reasonable kit and the shop may baulk at a refund because I am not a "professional" which by definition means work in a PC shop.

    I think I'll go with the mb first because the chance of it being the CPU is less likely, unless of course I zapped it during install so that will be my second point of call.

    Thanks for taking the time to reply.
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