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Motherbord No Power

Last response: in Motherboards
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May 8, 2011 8:30:49 AM

Hi,
I recently replaced several things in my three year old computer. I replaced the motherboard, memory, CPU, and graphics card. I kept all other parts like the computer case, power supply, hard drive, and DVD/CD drive. After removing those four parts and installing the new ones I connected everything back up and went to turn on my computer but there was no power, except for a blue light that turned on inside the case for a split second (it looked like the CPU Fan).

I used my computer with the old parts today so I know everything like the PSU and such was working before I installed the new stuff.

My computer specs are:
Motherbord: P67X-UD3-B3
CPU: Intel i5 2500k
Memory: Mushkin Enhanced Blackline 4GB (2 x 2GB) DDR3 1600 (PC3 12800)
Graphics card: Geforce 570
PSU: 750W PC Power and Cooling

More about : motherbord power

a c 156 V Motherboard
May 8, 2011 12:22:35 PM

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.
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%.

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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May 9, 2011 2:06:14 AM

I disconnected the power cable from the back of the power supply and held down the power button for several minutes. I then removed the battery on the motherboard for over 15 minutes and then put the batter back in and hooked everything back up but still no power except for the CPU fan light and another light by the memory that goes on for a brief moment.

I also took out the motherboard and made sure the standoffs under the motherboard were installed correctly and in the right spots. Finally, I tried to turn the computer on without the graphics card and switched out each memory stick but it's still not starting at all. Could this be a defective motherboard?
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a c 156 V Motherboard
May 9, 2011 1:01:47 PM

OK. To confirm:
You tried to boot with only CPU and heatsink, PSU, and case speaker installed and instead of any beeps, you got silence. Right?

That means the PSU, motherboard, or CPU is bad. The CPU is probably OK. If the PSU works in another computer, the problem is likely the motherboard.
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