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[HELP] Computer won't boot up after power outage

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October 6, 2010 4:50:00 PM

After electrical power outage, my computer won't boot up.

Here are the symptoms I have noticed.

1) When I power on, all the components including motherboard, graphic cards, hard-drive, CD-ROM, and fans get the power.

2) Monitor screen displays this message "No Signal", and does not display anything else.

3) I cannot get to the BIOS screen


Here are some things I have done to fix the problem.

1) Unplug all the cables and perform hard reset on the computer. I've also waited few hours before plugging back the cables.

2) Replaced graphic card with different one (graphic card test)

3) Removed 3 RAM (3 x 2GB), and tried single RAM operation (RAM test)
~ This is to test if any of the RAM was fried. Unless all 3 RAM were fried at the same time, this test failed. How likely is it for all 3 RAM get fried?

4) Replaced existing DVI monitor cable with another.


Based on few tests I have done above, I am assuming that the component that might have fried are listed below and I do not know how to check if they are fried or not. (Please tell me if you know how)

1) CPU

2) Motherboard

3) All 3 RAM at the same time


I am about to go to MicroCenter to purchase above components, and replace each one by one, but this method is too costly just to do the testing.

I have computer project due in couple days, and I am about to cry. This is my first time dealing with this type of situation, and I would appreciate if any of you could give me your wisdom to resolve this issue.

FYI, components that I am using are listed in my signature. I built my rig about 2 months ago.
October 6, 2010 6:56:26 PM

It's hard to say for sure. If all components are getting power, the fans are turning on, and if there are no beeps my best guess would be the CPU but truthfully it could also easily be the motherboard. When it comes to those 2 components it's incredibly difficult to tell without swapping one out. If it was the ram you should at least be getting a beep or something to show an error.
a b B Homebuilt system
October 6, 2010 7:25:00 PM

it could be anything. that's why you always use a good UPS and power strip.
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a c 122 B Homebuilt system
October 6, 2010 7:37:56 PM
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"Can't get to the BIOS screen" means that it is not POSTing.

Work 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.

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.

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...

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 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. 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.



October 6, 2010 7:45:22 PM

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