Probelms with Dell Dimension 8400

Ok so I have a Dell Dimension 8400 I'm trying to fix for a friend. I cleaned the dust out of but when I went to power it on it didn't do anything. I tried different cables and power sources. The light is green on the motherboard but nothing else. I shorted the psu and the psu fan turned on and seemed ok. I removed the ram, video card, and everything else one at a time trying to see if one of them was bad and still nothing. Is there a way to bypass the front power switch to turn the computer on? If that isn't the problem it has to be either the cpu, motherboard, or power supply (I'm thinking mobo). I found a motherboard on ebay for $48. I can't think of anything else to do other than order parts and replace them. Anyone know where I can find parts for this computer for cheap? I saw a used dimension that had everything but the cd drive and hard drive on craigslist for $50 but it already sold. Any insights or help would be appreciated. Thanks.
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More about probelms dell dimension 8400
  1. Have you tried removing the BIOS battery or using the shorting jumper for it ? Maybe the BIOS settings are screwed and need clearing.

    Otherwise sounds like you've exhausted the options and the mobo may be the cause.

    If you can find the exact motherboard you should be able to just use the existing Win installation without changing anything. I would say that was worth $48.

    Of course a nearly complete machine may be better value and if it's an older model they should be very easy to find -- I find Dells in the garbage around where I live.
  2. Update:

    I installed the new motherboard along with a new I/O panel board. Tested the power supply with a voltage meter and it read 5 and 12. I also shorted the p1 connector and put a case fan on it and it worked fine. So looks like it's not the motherboard or the power supply. I ordered a new cpu for $24 and if it doesn't work I don't know what the hell is wrong with this thing. Any other troubleshooting steps to try would be appreciated.

  3. What about the about the the button on the front of the case that you use to turn it on and off? Any chance it could be broken or lose? If so, how do I get the front panel off to look at it?
  4. I've just had a look at the beached Dell I have in my spare room and I can see why you're asking about accessing the ON switch -- they seem to have designed it to be difficult to get at.

    However, unless your friend has been especially brutal with the switch I very much doubt if it's faulty. So I think it would be simpler to look at the cabling between the switch and the mobo and see if there's any visible damage.

    While you are at it check the CPU fan is connected and (if poss check that it turns).
    If the fan is disconnected it may prevent the computer starting -- if it has failed the processor may be gone.
  5. Can't test the cpu fan but I know it's plugged in.
  6. No damage that I can see to the cabling that I can see.
  7. So I ordered a new front panel switch see:

    and a new cable that goes from the I/O panel to the motherboard:

    So now I would have a new motherboard, a new I/O panel and new cable to go to the motherboard, a new front ON switch panel and cable, and a new CPU. If I can't get this thing to turn on after all of this I have no clue what to do.
  8. I had a similar problem. When I removed the bios battery and shorted the negative and positive connections together for 30 seconds, the computer came to life! You need to try this!
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