Mainboard wont POST

D

duke

New member
Having a problem with a motherboard in a PC build I'm doing for a friend. It wont POST, or even give any warning beeps, it powers on for a second and the fans spin up but then switches off. I assumed it must be faulty hardware so I sent it back, although it was tested and found not to be faulty. They also suggested I may have purchased incompatible memory, which I haven't (according to the specification on their website). I have tried removing all components from the chassis and mounting them on cardboard to prevent any shorting although this did not solve the problem either.

Could anyone offer any suggestions as to why it wont POST?

The board is an ASUS P5B using a Core2Duo chip, with 2Gb of Corsair XMS2 PC2-6400.
 
What graphics card? P5B doesn't have on board iirc...

Also PSU could be dodgy?

What hardware was sent back and tested??? Where did you get it?
 
bought from ebuyer, graphics card is a geforce 7600, although the board should POST without a GFX card attached, or at least beep rather than simply powering down.

I tried using another PSU when it didn't work the first time so I was able to rule that out

edit: mobo and cpu were sent back
 
Ah ASUS P5B and Corsair memory ;) What have you got the memory set at in the BIOS...DDR2-800? Take the RAM off the auto setting if you have it set at that as the P5B reads the SPD info off the RAM incorrectly. Try a lower divider like DDR2-667 or even DDR-533. What Cas rating is it, Cl4 or Cl5? I have the same speed RAM in one of my other rigs and it was a right royal pita to get running properly. Look at your timings which should be 5-5-5-12 according to Corsair, but they prefer 5-5-5-15@ 1.9v. Failing that, head over to Corsair's forum and check out the compatability questions for ASUS P5B and XMS2 PC2-6400 here

I'm betting that the RAM is flakey and stuffed or running the RAM on a lower divider will fix the issue. If you are required to run it at the lower divider then RMA it, as it should run at DDR2-800 at those timings.
 
It's quite possible the RAM is fubar although I don't have any spare DDR2 that I can test with unfortunately. It would be a waste to RMA if I'm not sure the problem lies there as it would add an extra week to the ordeal :(.

Also as the board wont POST I have no way of entering BIOS and checking/setting the ram timings. I'm currently running Corsair XMS on a P4C with no problems at all.

The memory in question is CL5 and i quote from ebuyer
This memory has been verified to operate at 800MHz at the low latencies of 5-5-5-12-T1.
Click to expand...
 
Ah yes you did say that it wasn't posting my bad, I was in the middle of doing something else. Try taking the CPU out and running the board for ten seconds, and then insert CPU again etc etc, it resets the board to factory defaults. See if that does anything! I can tell you now though that the RAM doesn't run at those timings, even though Corsair state that it does on a P5B...

Check here
 
I'll give that a go! cheers

Gotta wait until 6 so I can go and pick up the returned goods from CityLink then I'll let you guys know how it goes.
 
I had a little worrying time when assembling my new C2D system today, I thought the CPU was duff but a little searching said to try bumping my RAM voltage up (from default 1.8 to the 2.2 written on the DDR2 module itself) and then all was OK.
 
Guys,

Just tested it again to no avail. It powers on fine with no CPU, fans spin etc although when the CPU is seated it simply powers on for a split second before powering itself off. To me this says that the PSU, RAM and Motherboard are all fine, and it is the CPU itself that is faulty. I made a quick video to show exactly what I mean:

http://youtube.com/watch?v=lMIQKxQsX28

I guess I'll have to RMA the CPU again, shouldn't Ebuyer have picked up on this though???

edit: is there any way to up the RAM voltage without access to BIOS?
 
Doesn't help that you don't have the heatsink on! ;)

That could be a factor, unless it doesn't boot with it on.

I hate when you get this kinda problem.
 
dont ever turn a computer on w/o the heatsink on it. maybe thats why it isnt booting, its turning off because its overheating
 
It doesn't boot regardless of whether the heatsink is on or not, I only had it off to demonstrate what happens
 
I just had a message back from ebuyer suggesting that I may have left out the "P4 cable" which supplies additional CPU power. I've never come across this before and AFAIK I haven't seen any additional power cable. Can someone point me in the right direction?

Cheers
 
Most modern PSU's come with a P4 power connector strapped on to the ATX power cable. It looks kinda the same but with only 4 connectors.

Check out this link which will provide a bit of a better explanation. Refer to the pic with '4 Pin Molex P4 12V Power Connector' next to it.
 
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