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System Troubleshoot

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January 13, 2011 10:15:30 AM

Hello,

I am having a problem with my computer not starting up when I turn it on. My drive power up and the fans spin so my stuff is getting power but it doesn't continue on to post or display anything. Is my MOBO dead are is there something else wrong?

More about : system troubleshoot

a b B Homebuilt system
January 13, 2011 10:31:25 AM

psu could be weak for gpu used, but double check MB has required cpu aux pwr input, and that gpu has aux power input(s) as well....
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January 13, 2011 11:10:05 AM

Being careful of ESD, try unplugging everything from the motherboard except for your CPU, RAM, and video card--anything then? This happened to me last week, and my PSU and motherboard had both randomly died (had to take it to a computer repair shop for diagnosis). :( 

Another thing you could try is breadboarding your build, in case something metal is shorting things out. See this thread for very detailed instruction for doing that and other ideas: PERFORM THESE STEPS before posting about boot/no video problems!
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January 13, 2011 5:55:16 PM

PSU is a 700 OCZ Game Extreme model. based on information coming from my ups. I am no where near that limit.

I have unplugged all my drives from the board but still no go.

Mobo has 24 bin power connector and an 8 pin aux power. GPU only has the standard 6 pin PCI express connector.

system has been running for well over a year and has been reliable. it wasn't until recently i noticed strange startup behavior. it became worse yesterday when i attempted to install a new 2tb drive
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January 13, 2011 5:58:32 PM

Do you have a PSU from another computer or a friend's computer that you could borrow to test if your PSU is the problem? My guess is that your PSU has died.
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January 14, 2011 9:21:09 AM

No I don't.

Update: I did pull everything out of my case and test my system with little luck.

While it was out I took a multimeter and probed out the big three voltages, 12, 5, & 3.3 while loaded. All voltages were present and within +/- 5% per ATX spec.

I turned off and unplugged everything over night. This morning, I decided to put everything back together to have a diagnostic test run on my system at a local computer store. For sh*ts and giggles I decided to power it up. FYI, the strange behavior that I mentioned earlier was the following. After acting strangely, in which fans and LEDs would pulse on and off before shutting completely off, I tried starting it up again to which it successfully started. BIOS voltage monitoring showed my big three present, however the 5 and 3.3 rails were a little low but within spec.

I am guessing my mobo is bad. Does anyone concur?
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a c 122 B Homebuilt system
January 14, 2011 10:18:49 AM

Not yet. :) 

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.

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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