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Need Help Troubleshooting. Home built system not booting.

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January 3, 2012 1:26:09 AM

Hi all,

I built a new computer just over a year ago and it has worked flawlessly since. That is, until I got back home after spending a couple weeks with the family for the holidays. I went to boot it up and it isn't working.

The lights on the mobo are all lit up and when i hit the power button everything seems to have power (HDD is spinning, fans all working (including gpu fan), etc), but nothing shows up on the monitor. No BIOS screen or anything at all.

I went through what I believe is the normal troubleshooting process. Unplugged all the millions of extras until I was left with only mobo, 1 stick of ram, processor, 1 video card, and keyboard. The problem persists. There seems to be power to everything and all the lights/fans work, but there's no signal to the monitor.

I was running 2 video cards w/ 3 monitors, so I've tried each video card separately and each video card with different monitors to eliminate the video cards and monitors from the problem.

I've also tried putting the ram in different slots, without it having any effect. I tried different ram modules as well.

So here's where I'm at: The PSU doesn't seem to be the problem because everything has power. The vid card doesn't seem to be the problem because i've tried two different ones that both worked last time i booted this computer. The monitor isn't the problem because I've tried multiple monitors. The ram isn't the problem because i've tried different modules in different slots. That leaves the mobo and the processor.

Anyone have any ideas on how to narrow it down further? Or any tricks/ideas I haven't thought of to get it to work?

System is as follows:

Mobo: gigabyte 890fxa ud5
processor: amd 1090t
psu: cougar cmx 1000W
vid cards: old geforce 9600 (x2) (only one installed at a time while troubleshooting)
ram: corsair xms3 (2x4gb)

Thanks for reading.
January 3, 2012 1:40:51 AM

I'm not an expert but if you left your computer unplugged during the holidays the motherboard could have been "discharged". I haven't really seen something like that but it's something one of my professors used to say.

If the CPU it's causing the problem the computer won't turn at all (correct me if I'm wrong)
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January 3, 2012 1:56:16 AM

Except for a milliamps from the 5 volt standby power supply inside the PSU, there's no power going into the motherboard when the system is turned off even when it is plugged in. So how could the motherboard "discharge"?

The following is an expansion of my troubleshooting tips in the breadboarding link in the "Cannot boot" thread.
http://www.tomshardware.com/forum/261145-31-read-postin...

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 (standby power supply): 5 volts always on. The green wire should also have 5 volts on it. It should go to 0 volts when you press the case power button (this is also a good way to test the power switch and the associated wiring), then back to 5 volts when you release the case power switch. 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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January 3, 2012 3:56:31 AM

Thanks for the quick reply. I have some new info.

I just realized I made a mistake. When I was switching from trying it with and without the boot drive, I was disconnecting the sata cable at the hdd instead of at the mobo.

Without a sata cable connected to the mobo (and with video card, 1 stick of ram, processor, and monitor hooked up) it does turn on, beep once, give the BIOS screen with the gigabyte logo etc, try to load operating system and say "DISK BOOT FAILURE....".

The strange thing is that once I reconnected the sata cable to the boot drive and mobo (exactly as it was when it wasn't starting up at all with no beeps, nothing on monitor, just lights and fans) it still goes through the loading screen, tries to load operating system and says "DISK BOOT FAILURE, INSERT SYSTEM DISK AND PRESS ENTER". I have tried it on both sata0 (which is sata 3) and a sata 2 spot so I'm pretty sure it's not the sata controller on the mobo.

This would be a hard drive failure right? It seems strange that it wasn't loading the BIOS before, and now it is, but should I just accept it as an excuse to order a SSD? I have other HDDs around, but they're all being used for media storage so I can't really use one as a tester boot drive. Do you think a new drive will solve my problems?

Thanks again for the help so far, and sorry I made a silly mistake which seems to have made such a difference.
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January 3, 2012 3:58:02 AM

Try removing the bios back up battery. Try replacing it also.
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January 12, 2012 11:46:23 PM

Best answer selected by naturalattrill.
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