Dimension 8400 won't turn on

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Dimension 8400 won't turn on

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The power button does nothing. It kinda doesn't even feel like there is a switch behind the button, but I don't use this computer often so I'm not certain. I thought it might be the power supply so I swapped that out. Nothing. When you first plug it in, the fan moves for a sec, then stops. There is a little green light that says on in the corner of the motherboard, but nothing else does anything.

Any ideas?

Verified Answer
  • bdesilva

    Ron, I checked the connection in the picture. Indeed it was a little loose, but re-seating it didn't help. The behavior didn't change.

    I'm trying now to be able to actually see the power button/switch itself. I've been able to get the back cover off but not the front (which of course is the one covering the switch. I cannot find documentation to assist in this. Do you nkow of any? I already broke a couple of the little plastic bits that hold some of the covers on and don't want to do any more damage!

     

     

    bdesilva 

    The power button and circuit board is one unit. Dell has not published a guide to remove the front bezel of the Dimension 8400, you can use this GUIDE, it's for an Optiplex GX50 Small Mini Tower, but the procedures are the same.

    Bev.

     

    If my answer was helpful, please use the 'Did this answer the question' and click: Yes
    Forum Member since 2001
    I am not employed by Dell

All Replies
  • Does the power button turn green or amber when you press it?  Do any of the diagnostic LEDs on rear of the tower light up when you press the power switch? The green LED on the motherboard means the system is getting some power.

     

    Check the front panel cable and make sure it's connected properly to the motherboard.  The location of the connector on the motherboard is shown here. It's possible the switch has broken and you would have to replace the front panel.

     

    Ron

    If this answers your question, please click  Yes  

    Ron

    Forum Member since 2004

    I am NOT a Dell employee

  • YES It could be the button. I think there should be an LED on on the button also. I would download the service manual...go to dell support site

    download drivers and info  select model...when you get to the driver page...on the left index select manuals, then on next page click green button on right "get manual"

  • Thanks for the quick response!

    Right now I've got the new Best Buy Dynex power supply hooked up. It has a toggle switch on the back. When I toggle the switch on, the fan comes on for a few seconds, the light on the front button illuminates then flashes green for the same few seconds as does the CD light. Then it goes off. When I press the button, nothing happens. I don't see any diagnostic lights coming on anywhere.

  • I should add that is the same behavior with the orig power supply in earlier today.

  • Ron, I checked the connection in the picture. Indeed it was a little loose, but re-seating it didn't help. The behavior didn't change.

    I'm trying now to be able to actually see the power button/switch itself. I've been able to get the back cover off but not the front (which of course is the one covering the switch. I cannot find documentation to assist in this. Do you nkow of any? I already broke a couple of the little plastic bits that hold some of the covers on and don't want to do any more damage!

  • I looked at the service manual,http://support.dell.com/support/edocs/systems/dim8400/SM/index.htm, but can't find anything to help me with getting to the power switch. Any suggestions?

    As I mentioned to Ron's response, I'm trying now to be able to actually see the power button/switch itself. I've been able to get the back cover off but not the front (which of course is the one covering the switch. I cannot find documentation to assist in this. Do you nkow of any? I already broke a couple of the little plastic bits that hold some of the covers on and don't want to do any more damage!

  • Instructions to remove the front panel on the 8400 were in a post on the old Dell forum before they came up with this "new/improved" forum, and I wasn't able to find them.  But hang in for a bit because I've asked the experts to see who remembers how to do it without  using dynamite or a blow torch. Big Smile

     

    Ron

    If this answers your question, please click  Yes  

    Ron

    Forum Member since 2004

    I am NOT a Dell employee

  • RoHe
    I wasn't able to find them

    there is a service manual...more then likely it is in there, as i suggested a few posts ago.   I have instructions on downloading the service manual

  • bdesilva

    Ron, I checked the connection in the picture. Indeed it was a little loose, but re-seating it didn't help. The behavior didn't change.

    I'm trying now to be able to actually see the power button/switch itself. I've been able to get the back cover off but not the front (which of course is the one covering the switch. I cannot find documentation to assist in this. Do you nkow of any? I already broke a couple of the little plastic bits that hold some of the covers on and don't want to do any more damage!

     

     

    bdesilva 

    The power button and circuit board is one unit. Dell has not published a guide to remove the front bezel of the Dimension 8400, you can use this GUIDE, it's for an Optiplex GX50 Small Mini Tower, but the procedures are the same.

    Bev.

     

    If my answer was helpful, please use the 'Did this answer the question' and click: Yes
    Forum Member since 2001
    I am not employed by Dell

  • going fixing my friends pc,

    Has the same problem, what i think it is, is.

    Blown capacitors in my friends pc there is 4 of them blown i think. they have a value of 1000uf at 10v.

    Have a look at yours and see if any of the capactiors have a rasied cap on the top.

    If you look at them most will be flat if some are rasied its usually a sign they have blow.

     

  • The last post in here was 2009,  boy am I lagging behind. Well anyway,  I surfed on in to look for an answer to this same problem, but none of the answers seemed to fit.  My dell did the same thing.   The power botton had this flashing amber light onetime after I shut the computer down, then wouldn't turn on again.  I tried a few things like pulling the plug on the thing waiting  a few minutes and then plugging it back in.  This worked for a time or two, but I encountered the problem often.  It seemed like the computer went into suspend mode and just wouldnt come out.  I finally solved it, by pulling the plug (turning off the strip) after shutting it down.  I havent encountered that problem since I started doing that.

  • Hi Manawela, After more then 6 years using my Dimension 8400 without any issue I have finally faced the same problem as everybody in here. My 8400 simply died 3 weeks ago and today my brother's died as well. I have just read your answer in here but I could not understand which plug you pulled turning off the strip. I'm trying to have both computers fixed so could you please be a little more specific about your solution? Thanks a million for your help.
  • @Rmcunha - "Pulling the plug" this case means switching off a power strip so the PC gets no power at all.

    What specific symptoms are your systems having ? "Died" doesn't tell us much. What color are the 4 diagnostic LEDs on rear of the 8400 when it won't boot? And what color is the power button, green or amber; steady or blinking?

     

    If this answers your question, please click  Yes  

    Ron

    Forum Member since 2004

    I am NOT a Dell employee

  • Hi Ron. Thanks a million for your prompt reply.

    That's exactly my problem. I have no lights at all at my 8400. Neither at the front power button nor at the 4 digit LEDs on the rear.

    What happened is that I had a power failure at home and when power returned I wasn't able to boot it back on and since then I was not able to boot it again.

    Looking inside the computer's case I can see that there is a green light at the mother board but nothing happens when I try to turn the computer on.

    I have read many posts complaining about the same problem but almost none of then explain how to fix it. Also the majority of the cases are related to the front power button blinking an ambar light instead of green which is not my case.

    Would you have any guess about what might have happened?

    Thanks for your comments and help.

  • By the way, just a last comment I pulled all the cables and connectors off the mother board and plugged them back on just to be sure they were all well plugged but unfortunately that didn't help much.