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Faulty Motherboard, Dodgy board?

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April 29, 2012 10:24:46 PM

Hi guys,
Am looking at a computer for someone but for the life of me can't figure out whats wrong it other than the board being knackered. It turns on by itself when plugged in and can not be turned off without unplugging. Also no screen is displayed and front LEDs do not light up at all. When powered the fans spin and the HDD and CDD seem to work.

It is a factory board from fujitsu.

I have checked/tried:

Different monitors, different RAM, checked CPU, changed/unplugged completely HDD, unplugged CDD, checked power pins, reset BIOS (removed battery and tried with the 2 pin connector), changed PSU.

If anyone has any other suggestions before I inform him he's gonna need a new one, would be gratefully received.

a b V Motherboard
April 29, 2012 10:48:32 PM

Could you give complete system specs, please? We would then be better able to help you.
April 29, 2012 10:58:03 PM

Sure,
Motherboard: Fujitsu D2660-A12
CPU: Intel Celeron 1.6GHZ
RAM: Samsung 512MB DDR2
Onboard Video out
HDD: Western Digital Caviar 80gb (SATA)

If you or anyone would like more info just let me know,
Cheers :) 
a c 156 V Motherboard
April 30, 2012 2:08:35 AM

Really sounds like the PSU. What brand and model were both power supplies? Did the second PSU come out of a working system - "known good" is the proper troubleshooting term?

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.
http://www.tomshardware.com/forum/261145-31-read-postin...

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. Breadboard with just motherboard, CPU & HSF, case speaker, and PSU. At this point, if you do not have a system (internal case) speaker, you really need one.


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, LED's, or fan activity:

Check for line power at the PSU input. Extension cords, power strips, and power cords do fail.

If you have power and no beeps, suspect components in likely order are PSU, motherboard, and CPU.

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 green wire should read 5 volts and drop to around 0 volts when you press the case power switch.


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.
!