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Motherboard issue

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April 20, 2011 6:54:30 AM

Hi,

My motherboard is Asus P5q, from yesterday onwards my system is not getting started, I looked into it & the only change is the greed LED/power_SD insead of being stationary it started blinking, can some one pinpoint what could be the problem & a work around is possible or point me in right direction in which i can figure out whats wrong with it.

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a b V Motherboard
a b Ĉ ASUS
April 20, 2011 10:32:31 AM

No fans start, no noise, nothing, right?
Then unplug everything from the MB except the PSU, one stick of RAM, fans, and video card (if any), see if it boots. if not the PSU is bad.
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a c 156 V Motherboard
a b Ĉ ASUS
April 20, 2011 11:36:55 AM

Work systematically through our standard checklist and troubleshooting thread:
http://www.tomshardware.com/forum/261145-31-read-postin...
I mean work through, not just read over it. We spent a lot of time on this. It should find most of the problems.

If not, continue.
The following is an expansion of my troubleshooting tips in the breadboarding link in the "Cannot boot" thread.

I have tested the following beep patterns on Gigabyte, eVGA, and ECS motherboards. Other BIOS' may be different, but they all use a single short beep for a successful POST.

Breadboard - that will help isolate any kind of case problem you might have.
http://www.tomshardware.com/forum/262730-31-breadboardi...

Breadboard with just motherboard, CPU & HSF, case speaker, and PSU.

Make sure you plug the CPU power cable in. The system will not boot without it.

I always breadboard a new build. It takes only a few minutes, and you know you are putting good parts in the case once you are finished.

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. Remember, at this time, you do not have a graphics card installed so the load on your PSU will be reduced.

If no beeps:
Running fans and drives and motherboard LED's do not necessarily indicate a good PSU. In the absence of a single short beep, they also do not indicate that the system is booting.

At this point, you can sort of check the PSU. Try to borrow a known good PSU of around 550 - 600 watts. That will power just about any system with a single GPU. If you cannot do that, use a DMM to measure the voltages. Measure between the colored wires and either chassis ground or the black wires. 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. Tolerances are +/- 5% except for the -12 volts which is +/- 10%.

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.
http://www.youtube.com/watch?v=5FWXgQSokF4&feature=yout...

A way that might be easier is to use the main power plug. Working from the back of the plug where the wires come out, use a bare paperclip to short between the green wire and one of the neighboring black wires. That will do the same thing with an installed PSU. It is also an easy way to bypass a questionable case power switch.

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.

If the system beeps:
If it looks like the PSU is good, install a memory stick. Boot. Beep pattern should change to one long and several short beeps indicating a missing graphics card.

Silence, long single beeps, or series of short beeps indicate a problem with the memory. If you get short beeps verify that the memory is in the appropriate motherboard slots.

Insert the video card and connect any necessary PCIe power connectors. Boot. At this point, the system should POST successfully (a single short beep). Notice that you do not need keyboard, mouse, monitor, or drives to successfully POST.
At this point, if the system doesn't work, it's either the video card or an inadequate PSU. Or rarely - the motherboard's PCIe interface.

Now start connecting the rest of the devices starting with the monitor, then keyboard and mouse, then the rest of the devices, testing after each step. It's possible that you can pass the POST with a defective video card. The POST routines can only check the video interface. It cannot check the internal parts of the video card.
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April 20, 2011 7:29:13 PM

Hi,

Thanks for responding, let me clarify the situation more, the PSU is cooler master 500 +, system was working fine, there is no system beep & nothing just the green led(power_sd) is blinking, i can't borrow PSU i have to buy a new one just to check, I also tried to remove all connections & then tried same result no system boot sound or any sound at all, can PSU be damages since the blinking green LED show that power is been transmited to motherboard.
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a c 108 V Motherboard
a b Ĉ ASUS
April 20, 2011 7:40:47 PM

have you tried jsc's breadboarding guide yet?
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April 21, 2011 10:30:20 AM

Hi,

I have not preformed all the steps but there are many steps that are for newly installed system. Mine was wroking for last 17-18 month & i have tried reconnecting the power that did help, I will preform others steps & let u know in case that helps. Meanwhile if there is no beep in that system what could be the general cause, it can't be less powered PSU since it was working earlier & i have only add a new hard disk in recent past & after that also it worked of a month.
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a b V Motherboard
a b Ĉ ASUS
April 21, 2011 2:13:48 PM

ripudaman said:
...it can't be less powered PSU since it was working earlier & i have only add a new hard disk in recent past & after that also it worked of a month.
Incorrect. The PSU can fail at any time, and it can be extremely difficult to diagnose.
I am not saying yours is definitely bad though, but it has a higher probability.
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a c 108 V Motherboard
a b Ĉ ASUS
April 21, 2011 6:00:31 PM

If your motherboard has a speaker embedded or if you connected one, then the absence of beeps indicates possible mobo failure. At the bare minimum, with a speaker attached, the mobo should emit at least one short beep. This short beep is indicative of a successful POST. That is of course, unless you turned off that function from your BIOS.

On the other hand, if you did not install a speaker, double check to see if your mobo does have one. If not, get one, as it could help in diagnosing the problem.

In response to your logic that breadboarding applies to new builds, that is not always true. A short circuit isn't limited to when a computer is first built, but rather that is the typical time when a short occurs. Heat causes expansion. Some parts may now have their individual parts (resistors, capacitors, etc) touch metal when it previously may not have. Again, these are just theories, but unless you rule them out, you're left with uncertainty.

While you're inspecting the parts inside your computer, or if you do perform the breadboarding, be sure to check for any physical signs of damage, like bulging/leaking capacitors.
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April 25, 2011 6:14:06 AM

Best answer selected by ripudaman.
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April 25, 2011 6:14:52 AM

Hi All,

Thanks for the help...its working fine now
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!