Motherboard Replacement

Posted on 2005-04-07
Last Modified: 2010-04-25
My brother asked me to fix his E-machine that mysteriously quit turning on. He would push the on button nothing would happen.  He brought it to Best Buy where he purchased it and they said the motherboard was bad. Gave him an estimate to send it back and fix it, his warranty was up, too rich for his blood. He asked me to fix it.

I put it on my bench at work. Plug it up, hit the power button nothing happens. Left the room. Came back. Power supply fan and CPu fan are turning. Nothing is coming on. Can't get it to come back on after that. I take the BB guys diagnosis. Bad MB. Order new MB from Emachines. On backorder. Get it 3 weeks later today.  Put in the new motherboard. Connect everything up. Plug power cord into machine and the thing immediately starts up (w/o pushing the power button), can hear HD spin, but LOCK light on KB flash, no PC beeps, nothing on the monitor.  Removed everything except the power. Same result. Bench built it, same result. No bent pins on the CPU. CPU only fits in the socket one way.  A) Why is this thing immediately firing up without pushing the power button? B) What the heck is wrong with this thing besides it is an Emachine.  I've invested $165 in a new proprietary MB for this thing. Trying really hard to keep costs down because my brother is thrifty. Also he needs this thing to do his taxes and I've had it for 3 weeks.  HELP!!
Question by:kkpsiguy
    LVL 14

    Expert Comment

    Are you sure that youv'e got the connectors from the case connected correctly. Usually they are small 2 pin type of connectors and are easily put in the wrong way round or mounted on the wrong pins. You're problem sounds like the power on pins are shorting.

    Another idea is to reset the bios, either with the CMOS connector or just remove the battery for a few minutes.
    LVL 6

    Expert Comment

    Did you know the E stands for EVIL?

    Anyway, I have had similar probs before all with different causes.

    Firstly reset the bios using the jumper on the motherboard. Setting optimized defaults is not the same thing.

    Next thing to check would be the front panel connectors for the reset switch, power switch etc. Make sure they are all on the correct pins.

    If that's all fine and you still get the problem then remove the connector for the reset switch and plug the connector for the power switch in its place (ie: power switch connects to reset pins). Then switch on and if it works properly and you can turn the PC on and off with the reset switch you know that your case has a dodgy power button.

    Failing that, do you have a spare PSU floating about you can try.
    LVL 13

    Expert Comment


    Putting $165 into a new motherboard for that machine was a mistake.  Better to buy a new case, power supply and motherboard, you can move everything else.

    Make sure that the mother board has a CMOS battery, and then remove it (with the comptuer UNPLUGGED), and clear CMOS (usually, short some jumpers on the motherboard), then reinstall the battery and see if it fixes things.

    I'm not sure I buy that this is a motherboard problem rather than a power supply problem.  If the motherboard connector is standard (and it probably is), you can try a generic ATX power supply.  Also, I do presume that you properly connected the power supply to the motherboard (both the main connector and the ATX12V connector).  Double check, as well, the other case connections to the motherboard.


    Author Comment

    Here's the deal. Put the old MB and the new MB on the bench outside a case and too the necessary static precautions. Plug up the old MB with nothing in it and nothing plugged into it execept the the main power connection and the ATX connection. Nothing happens when I put the plug into the power supply. Power supply DOES NOT come on.  Exact same scenario with the new MB. Put the plug in the power supply, it immediately whirs to life. Ideas? I need to sort this out before I can even begin to eliminate anything else.  Thanks.
    LVL 69

    Accepted Solution

    It sounds like pin 14 and ground are shorting out somehow:  This would point to a defective motherboard, since you know it isn't shorting on the case.
    LVL 13

    Expert Comment


    In general, the power supply should not start until the power button is pressed.  However, some BIOS' have a CMOS setting as to what to do after recovery from a power failure, which has an option to automatically start-up (or, if you prefer, "restart").  Remove the CMOS battery, and clear CMOS -- on both motherboards.

    Author Comment

    I shipped the new MB back in exchange for another one. We'll see if this fixes the problem or I'll have wasted a few more days and shipping fees. I cleared the CMOS and you shouldn't have to do that on a new MB anyways. The old one is dead. I will distribute point after the next new one comes in and if it works.
    LVL 87

    Expert Comment


    No comment has been added to this question in more than 21 days, so it is now classified as abandoned..
    I will leave the following recommendation for this question in the Cleanup topic area:
    Accept: Callandor

    Any objections should be posted here in the next 4 days. After that time, the question will be closed.

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