Z68 mobo Core i7 2700k no post!

P

Poweraid

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Mar 29, 2011
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I'm really at an absolutely loss here and could use some advice. I'm an experienced builder, no exaggeration at least 100 complete desktops i've built in the last 15 years so I like to think I know what I'm doing, but here goes :p

Asus P8Z68-V motherboard (1155 / z68)
Core i7-2700k (also tried a brand new Core i3-2100 since the asus website says it works with the virgin BIOS ver)
16GB Corsair Vengeance 1600 1.5v
Zotac GTX560 ti (although I left this disconnected since it has integrated graphics, tried it anyway just for kicks)
900W Antec PSU

Okay, I always start my builds with the bare essentials... motherboard, cpu, ram, power supply. I didn't install the vid card (except later for troubleshooting) since the mobo utilizes the on-die HD graphics and has a vga/dvi/hdmi port. System powers on for a few seconds, then shuts off and does this repeatedly. Things I've done so far, none of which provided any results besides what I just described...

- verified this model RAM is on the supported RAM list for this model mobo
- verified the RAM is functional using my other desktop
- tried individual sticks of ram, one at a time, in each of the 4 slots
- grabbed my ddr3 4GB module from my other desktop which 100% works and is also on the supported ram list. tried it in all 4 slots, no change
- reset cmos (many times)
- tried a known good 700w psu
- tried with my known good video card
- reseated CPU, verified no bent pins on the socket and no debris (several times)
- tried every possible combination of disabling/enabling TPU and EPU

- after doing all that, RMA'd the mobo and received a brand new one
- exact same symptoms. at this point i know 100% for certain that the RAM, power supply, and video card are fully functional. only thing left was the CPU
- just for kicks, I checked the list of supported CPU's for this model mobo, and went to fry's to grab a brand new Core i3-2100 to test with since this is verified to work with the virgin BIOS from the factory
- exact same symptoms with the core i3 2100... powers on for a few seconds, shuts off, does this repeatedly
- repeated all the previous steps concerning resetting BIOS, different ram slots, etc using the Core i3

- thinking there might be a major compatibility issue somewhere, i went back to fry's and picked up a cheaper Gigabyte Z68AP-D3 mobo
- EXACT SAME SYMPTOMS
- tried both processors, 3 different model ram modules, all on the approved ram list
- two different power supplies
- onboard and my gtx560
- reset cmos

I get absolutely the exact same symptoms every single time no matter what configuration I use. I literally spent 6 hours doing every possible combination of cpu, ram, motherboard, psu, and video card and get the exact same results everytime. What else is left to do?? Driving me crazy, never been stumped like this before. I can always find the issue through process of elimination, but there's no common denominator here!

Any help/advice/exorcism is appreciated
 
Wow, um, that doesn't leave a whole lot. What about a standoff in the case that may be not needed and touching the back of the motherboard, perhaps shorting something?

A case fan that is shorted causing the PSU to to freak out? ( never seen this happen but worth a mention I guess )

Insulation on the wires from the case to the mobo (pw, reset etc etc) has worn off and is grounding out on the case?

Do you live next to a house sized electromagnet?
 
Few other things ~ how about the main power cord to the psu, is it old? new? Try another, or try another outlet in the house.... different or no surge protector.

If you are assembling the rig without a case, I have heard of people who had issues with the PSU not getting a good enough ground if its just sitting on a desk and not attached to a case. Personally i've never had that problem but just tossing it out there......
 
lol i might need to check on the neighbor about the electromagnet theory :p

As far as the shorting out, the Asus board in particular has a fairly thick backplate for the chipset passive heatsinks, but i made sure it wasn't touching. For the Gigabyte board, i just used a nonstatic workbench and connected everything there so definitely not a short

Just for kicks, I tried your theory about the outlet. I used the same outlet my current desktop is plugged into, tried the wall outlet bare with no surge protector, same thing.

I just thought of something, maybe a stretch... both CPU's i tested in the Asus board first. Could the possibly defective board hae shorted out the cpu and causing it to fail on the new gigabyte board as well? o_O
 
Yes i think the power cord/outlet may be a problem as well, please report back if you fix this really strange issue!
 
Double check to make sure there isn't an unused standoff still in the case that would be touching the back of the motherboard, not just the backplates for the heatsinks. I've noticed that some atx boards use slightly different mounting locations and when you pull an old mobo and put the new one in, the unused one needs to be pulled. Im sure you would have noticed that tho.

As far as the asus board nuking the cpu, I guess, but unlikely if you RMA'd one already. Unless they sent you the same one back, lol.

Try pulling EVERYTHING (no cpu, no ram etc) just the psu and the mobo and see if it will power on and stay on. I realize it will not post, but it will be interesting to see if it at least stays on.
 
8 pin Aux +12V connector for CPU at top in?
PSU rocker on 1? Plug all the way in PSU as far as it can go?

You also need to try a more serious cmos reset - batt out, jumper shorted, PSU unplugged, 4 hours minimum.

You could go to Fry's and but a $10-$15 Logitech wired KB and mouse USB 2.0

you left off something very important - HSF
lemmee guess - CM 212+ or Corsair H-XX
You must try with Intel stock CPU HSF and make sure plastic pins are all expanded underneath

Fwiw: all the Z68 V-Pros I have built came as PCIe/PCI set as default in bios, which means mobo will not boot to onboard vid because bios is not set to iGPU

Looping in resets means something cannot be tolerated or fixed by bios

This also could mean HS fan connector is not on right header, or perhaps fan is dead or has too low RPM in minimum mode. These mobo bios default to 600RPM Min for CPU

I would also try the cheapest PCI VGA vidcard I could find
I always keep one of these around for troubleshooting
http://www.geeks.com/products_sc.asp?cat=861
 
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One last trick that worked on some of my older systems after a cmos reset ~ when the machine is off and unplugged, hold the power button on the case for 10-15 seconds. That used to get one of my old crappy psu/mobo combinations to boot back up once plugged in. Best guess is that it zaps power from the remaining capacitors on the mobo/psu. Truthfully im not sure exactly what it did, but it worked on one of my old x64 setups.
 
Have you tried pressing the Mem OK button before POST?

Wiggle your 24 pin power connector. On my ASUS P8Z68V-Pro sometimes it seems to get loose for some reason (heat?) and then it will do boot loops unless I go physically wiggle it.
 
Probably a power button issue, if it powers for while(around 5 secs) than turns off again, the power button when pressed, holds the electrical contact inside connected although it may appear it is in its position again.
 
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