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Repair motherboard

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  • Chipsets
  • Motherboards
  • Power
Last response: in Motherboards
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April 7, 2011 9:30:38 AM

Hello,

the motherboard cannot raise the voltage up when i turn on. I have checked the power suplly. that it's still working. Why? what i should do?

More about : repair motherboard

a c 156 V Motherboard
April 7, 2011 10:32:51 AM

What motherboard? Does it have a locked BIOS?
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April 7, 2011 10:23:45 PM

Unless you have a working system to swap parts back and forth with this may be futile. If you have another pc, then your best bet is to carefully (and away from high static / liquid spill area's) exchange the compatible parts until you find the point of failure. I would always start with the power supply. If you do not have another system fear not for all is not lost.

For the purposes of powering on your system, you should manually short the power jumper on the motherboard instead of using the switch on the front of the case. This way we can eliminate if the case button has died. You can accomplish this easily with a light touch from a screwdriver. Just make sure you don't short the wrong pins.

The first spot to check for power problems is always the cable and the power supply. Right next to where the cable from the wall connects to the computer there should be a small red switch. One side will say 110, the other will say 220. Manually change its position to ensure its completely clicked onto the correct voltage. (US uses 110) Make sure the power cable is securely connected. Try powering on your system.

Still no go? Maybe you have some bad capacitors or a bad voltage regulator on the board. Do you have a chalky dusty buildup on top of the capacitors near your CPU? =
If the tops of any capacitors are swollen or have boiled over then they are shot and will need replaced (or replace the whole board). If you don't see this either then its time to buy a new system, or bring it to a repair shop. Good luck!
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a c 156 V Motherboard
April 8, 2011 8:45:05 AM

akyas,
English does not seem to be your birth language, so more questions and a suggestion:
What parts do you have in your system - PSU, motherboard, CPU, video card, drives?
Like rolli asked, is this a new system or an old system that stopped working?
Does the system pass the POwerup Self Test (called a POST) with a single beep?
If not, what turns on when you press the power switch?
What else happens or does not happen when you try to turn on the computer?

And the suggestion:
Try to have a friend who speaks better English help you with your post.

If your system will not boot (in my reply before, I thought you had a different problem), the guide that rolli linked to is an excellent place to start looking for what is wrong.

After that, this may help:
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%. If you have a white wire (many modern PSU's do not), it should be -5 volts.

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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