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mobo won't boot after upgrading cpu

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calpolyarc

Registered
Joined
Feb 19, 2009
I have an asus p5b mobo... today i replaced the psu (to an Antec 500w Earthwatts) and the cpu (to a q9650). According to the Asus website the p5b board is compatible with the q9650. So I hooked everything up, plugged the power cord into the psu and then hit the power button.... nothing, silence. The green LED on the mobo is on so I assume it's getting power. I cleared the CMOS by removing the battery and by moving/moving back the RTC/CMOS jumper. I hit the power button... nothing. I remove all of my RAM except 1 stick... hit the power button... nothing.

Then I install the old cpu and old psu and go through all of the same steps and.... nothing, even though the system was working perfectly earlier today.

What could be the problem? I assume that just because the green LED is on that doesn't mean the mobo is in 'perfect' working order? Are there any other possibilities? Anything else I should try? :bang head

Thanks.
 
I forgot to mention that I did update the bios before installing the new cpu.
 
You need to make sure that you've got the 24 pin ATX plugged in, and then there is usually two other power connections needed that are 4 pins a piece. Some mobos only have one of the 4pin connectors though, either way check it. Also reseat your ram, try different ports... reseat the CPU and make sure it's correctly aligned. And as a last resort, unplug everything from the mobo such as hardrives/cdroms/soundcards/modems... leave nothing but the videocard/mobo/cpu/ram. If it boots up then let it boot up and go into BIOS and set defaults. Then add one piece of hardware at a time until you find the problem.
 
also if its in a case take it out and bench test on a box or anti satic bag to make sure theres no shorts and clear cmos by unpluging power pulling cmos battery and putting cmos jumper on 2/3 or as manusl says for ten min.s or so
Rich

btw:welcome: to the forum
 
As other have said previously, check all of your power connections from the power supply. Also, double check your front header connections. Maybe the power button for the case is hooked up to the wrong pins.
 
That sounds like a bad power button. Try jumping the leads on the mobo where the case power button connects.
 
jump starting with the old cpu and psu didn't work... I can hear a 'click' in the psu telling me that I've made the jumpstart connection but as I hold it there nothing else happens. And this is with the mobo out of the case and only the essentials connected: 4 pin power, 24 pin power, fan power, cpu, fan, video card, 1 stick of ram.
 
Did the system boot after the flash (as MARCI asked in post #4)?

If it did I would try another type of ram if you have some available. I've seen boards refuse to post when everything was OK hardware wise, the ram swap usually fixes it.
 
I'm ashamed to even say what the problem was but I will just in case it helps someone in the future...

I had the floppy drive power cable from the PSU plugged into the 'power fan' pins on the mobo :screwy: For some reason I had it stuck in my head that the psu needed to supply power separately to the fan. :bang head

And this is with the mobo out of the case and only the essentials connected: 4 pin power, 24 pin power, fan power, cpu, fan, video card, 1 stick of ram.
See where it says 'fan power' and also 'fan'... yeah that's the problem, lol. If only I had a floppy drive that cable would've been spoken for!

:mad: .... deep breath, time to move on...

Thanks everyone for your time and suggestions.
 
Yeah been there done that too a few years ago... hard drive actually caught on fire!
Thanks Marci :)
 
Glad it all worked out.... I upgraded my Graphics card Tuesday evening, powered everything up, and heard a loud pop, and the magic smoke came from my PSU... I overcompensated with the replacement.. Luckily nothing else bit the dust

I notice you're running a 'generic' PSU.. I assume it's a free one that came with your case or something? I'd swap that out for a more reliable psu as soon as I could.. It'd be a shame for a free psu to spike a mobo/cpu/ram etc..
 
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