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Is the motherboard fried?

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July 27, 2010 12:29:15 AM

A storm came through recently and lightning ran into my mother in laws pc. Now it will not power up at all. The green light on the back of the power supply would light up, but hitting the power button to the pc resulted in nothing. So I bought a new psu and hooked everything back up as before. But still nothing happens when hitting the power button. Could this be the result of the motherboard being fried? Or is it the result of something else? Would appreciate any feedback.

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July 27, 2010 12:38:34 AM

Well, yes. If replacing the PSU did not work, then it probably did fry the motherboard. Make sure that whatever you do end up doing, ends up on a good surge protector. The reason it sounds like its the motherboard is because of your comment of not having anything happen when you hit the motherboard. This is a good indicator, because if the motherboard is property seated with the power supply unit, at minimum, a light on the board (granted it has one) or a startup fan would have done something.

NOTE: When you plug a PSU unit into a motherboard, do not have it turned in the ON position until after it is seated. Additionally, once you do turn it on, check for a light on the board indicating that its acquiring power from the PSU (good, bad, or indifferent)
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July 27, 2010 12:54:10 AM

Yea I figured it might be the motherboard. No fans or anything will function when hitting the power and their is no light on the motherboard to go by either. Time to look for a new motherboard. Thanks for the input.
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a b V Motherboard
July 27, 2010 1:17:06 AM

Before you condemn the motherboard try removing any cards fitted in the computer particularly any modem or network card fitted. A lightening strike often damages the modem card if it is connected to the phone line.
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July 27, 2010 1:38:50 AM

I will give that a try, didn't think to do that before. Would be an easier fix than putting another motherboard in. Luckily it doesn't have a lot to remove.
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a c 156 V Motherboard
July 28, 2010 7:08:21 PM

Work through our standard checklist and troubleshooting thread:
http://www.tomshardware.com/forum/261145-31-read-postin...
yes? I mean work through, not just read over it.

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

The breadboarding thread has a paragraph about how to build and test a PC in stages.

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

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.

At this point, you can sort of check the PSU. Try to borrow a known good PSU. 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...

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 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 or long single beeps indicate a problem with the memory.

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.

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.
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July 29, 2010 12:22:12 AM

I have the exact same problem. I replaced the motherboard and it still not working. I've never had one fail to power up anything. Tested and retested the psu. Is is possibility the CPU would cause this also? I would think bad CPU would show some signs of life???
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