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Not posting. Switching on, off, on again in a loop

  • Gigabyte
  • Motherboards
Last response: in Motherboards
March 7, 2010 4:51:08 PM

Windows XP 32
Antec 300 case
Gigabyte GA-P55-US3L mobo
Intel i5-750 CPU
Nvidia Geforce GTX285 (by Gainward)
Corsair VX550W PSU
Corsair (2x1gb) TwinX XMS3 DDR3
Samsung 500gb HD502HJ SpinPoint F3
LiteOn IHAP122-19 22x DVD+and-, 8xDVD
Saitek PK 02AV Eclipse II Wired Keyboard
Kensington Wireless Laser Mouse
22" Digimate - DGM L-2262WD Black, Widescreen LCD

All new parts.

Here's the problem;

When I turn on the power the MOBO leds all come on, the fans all spin up, the optical drive begins to star and the hard drive begins to spin up but after 1-2 seconds it all shuts down. If I wait, touching nothing it starts up again. It continues to go through this loop until I turn off the main power at which time it will attempt to go through the cycle again for a split second before finally turning off (must be some residual power in the system).

I've stripped everything out and have tested the PSU by shorting the green wire to a black. It powers up and stays on.

And then one at time I've connected each of the following to the PSU, disconnecting before trying the next;

I've connected the optical drive and that comes on, opens and shuts ok.
I've connected the hard drive and that spins up ok.
I've connected the GPU and that starts up ok.

Then I reseated the CPU and fan, new thermal paste and all. I connected the 24 pin MOBO cable and the 4 pin ATX to the MOBO and switched on. It goes through the same loop.

I had no RAM inserted during that test so I tried it with the RAM, singly and the pairs in all combination, in all the slots. It made no difference.

To me it seems obvious that it must be either the MOBO or CPU but what do I know. I have no experience at this and I've never assembled my own computer.

What does everyone else think and is there anyway to test these things.

I don't have another system I can try either in and though under warranty it's been so expensive I have no money at the moment to go through the returns process.

Does anyone know any way to narrow it down and could I remove the cpu but keep the fan connected so I've only got the MOBO, 4 pin ATX and 24 pin MOBO connected? Or would this damage the MOBO in some way?

More about : posting switching loop

a c 178 V Motherboard
March 7, 2010 5:14:17 PM

Try this:
Disconnect anything USB, except, if applicable, kbd & rodent;
hold power switch depressed until MOBO finally shuts off completely;
power down at PSU switch, or, if no PSU switch, pull the plug;
while 'unpowered', momentarily short the CMOS_RST pins with a jumper, or a steady hand and a small, flat screwdriver blade;
remove all but one DIMM, in slot DDR3_1, second from CPU;
power back up - if able, enter BIOS;
do a "Load Optimized Defaults" from first BIOS menu;
<F10> to save, exit, and reboot;
power back down, and add remaining DIMMs...

If this procedure doesn't work, you're at the spot where you really need a case speaker - it's the only diagnostic info available at that point:

Oh - and, pulling the CPU won't hurt anything - but won't show you anything either - everything the MOBO can do at all is dependent on the CPU's fuctioning; if we sawed open your head, and removed your brain, pretty much nothing that's left would function at all :pt1cable: 
March 7, 2010 9:23:30 PM

Done everything suggested already and can't enter BIOS so looks like final option is case speaker. Once I've sorted that I'll post back.

So no way to know if it's the MOBO off CPU shutting off the PSU then allowing it to restart ect. That's all I wanted to do with the suggestion to remove the CPU. Thanks anyway.
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a c 178 V Motherboard
March 7, 2010 9:53:03 PM

One thing I often suggest when testing PSU is to examine the status of pin 8 (PWR_OK - gray); if it's not coming high, your rails can all be good, and board still will not start, and keep resetting...
March 7, 2010 10:03:39 PM

I'll have a look at that tomorrow. Bit late at the moment to be getting everything out again. Just noticed another post on this forum that says with the same MOBO it was his ram and have been told that a MOBO with no ram attached would give the same symptoms as with broken/not recognized ram. You learn something new . . . as they say. Will have a look at the voltage tomorrow and get another 1gb of ram to test in the MOBO. Will let you know the result. Thanks for your help.
a c 178 V Motherboard
March 7, 2010 10:50:14 PM

The 'trick' to the speaker is:

The following Award BIOS beep code descriptions may help you identify possible computer problems.

1 short: System boots successfully
2 short: CMOS setting error
1 long, 1 short: Memory or motherboard error
1 long, 2 short: Monitor or graphics card error
1 long, 3 short: Keyboard error
1 long, 9 short: BIOS ROM error
Continuous long beeps: Graphics card not inserted properly
Continuous short beeps: Power error

(page 119 of your manual)

...even if you are just getting the single "OK" beep, whether you get it every reboot, or every other one, or not at all - each tells us something unique about the (possible) cause of the trouble...
March 13, 2010 8:19:17 PM

Might also consider something simple but often overlooked....a 2 dollar front case on/off button. I had an issue like this where it would attempt to start, then shut off, rinse and repeat. The on/off front case power button was going bad, replacement fixed my issue. hARD to find. I found the power switch at someplace called
a b V Motherboard
March 13, 2010 8:29:48 PM

This is a common problem with some gigabyte motherboards they get stuck in that loop sorry to say you are most likely gonna have to return it.
March 13, 2010 8:53:26 PM

It certainly seems that way from all the other forums I've read. It's on its way back to the company I purchased it off. They've asked me to return the psu, cpu and ram with it. As long as they can't start it, it wont cost me anything. Just waiting to see what they say.
March 19, 2010 3:47:56 PM

I've returned the MoBo, the CPU, the PSU and the RAM back to the company for testing and they found the MoBo was faulty.

Just waiting for the replacement Mobo and other parts to be returned. Thanks for any help given folks.