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Dell XPS 400, mb light on green, but not power

Posted on 2009-05-05
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Last Modified: 2013-11-09
Hello,

I have a Dell XPS 400, the green light comes on on the motherboard, but when I press the power button, nothing at all happens, I've tried it w/ another power supply w/ no results.

Any suggestions?

Thanks
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Question by:PavPPZ1
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Expert Comment

by:chilternPC
ID: 24308272
disconnect all extras and just leaft the screen attached and switch on. then if nothing
then disconnect and remove the RAM and try again - it should beep twice.
if nothing then its either the mobo or the CPU or both.
check the capacitors on the mobo and see if they are bulging (they should be flat topped)
if bulging - dead mobo
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Expert Comment

by:alecg13
ID: 24308304
There might be a problem with the motherboard. Have you check (if you know how) all the connections on the motherboard on the inside of the computer to see if there are any motherboard connections unpluged. You might also want to try holding down the power button when you try to turn on your computer. Otherwise, you might want to consider contacting Dell and see if they can repair it.

Hope this helps!
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Author Comment

by:PavPPZ1
ID: 24308344
The capacitors look okay from what I can tell, but I tried what you said, and it still won't turn on, its as if the power button doesn't work at all or something.
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by:chilternPC
ID: 24308474
sorry must ask - you have connected 2 power leads to the mobo and the switch leads to the mobo?
if so...
sounds like a dead mobo.
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Author Comment

by:PavPPZ1
ID: 24308857
yeah they're on, and the green light is lit
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by:jamietoner
ID: 24310317
Could be a bad control panel or control panel cable. This is a PITA but try and trace the power button wires on the ribbon to where it plugs into the motherboard and short the 2 pins with a screwdriver and see if it will power on.
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by:chilternPC
ID: 24313805
could be static - sometimes I've found with dell, - power supplies not working and then after they have been earthed and discharged they work again.
do you have a power supply tester ?(about £10 in the uk)
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by:nobus
ID: 24315662
that's when they go into protection (of ten caused by an overload) some get out quick, or automatic, some have to bleed.
if you want to short the power pins, check if this helps  :
Dell-Power-on.doc
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Author Comment

by:PavPPZ1
ID: 24318312
I've tried a different power supply, it does the same thing
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by:chilternPC
ID: 24319677
sounds like the mobo is brown bread (dead)
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Author Comment

by:PavPPZ1
ID: 24325918
alright, i'm going to order a replacement motherboard, i'll let you know how it works out
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by:jamietoner
ID: 24328755
Did you try the control panel trick? A control panel is alot cheaper than a motherboard.
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by:PavPPZ1
ID: 24329220
What is that?
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by:jamietoner
ID: 24329503
On most dell systems the power button connects to it. Try tracing the power button wires to where it plugs into the motherboard(usually a ribbon cable) and short the 2 pins quickly, if the system turns on the powert button and/or control panel is bad, if it still doesn't turn on then it's the motherboard.
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Author Comment

by:PavPPZ1
ID: 24329636
There is one ribbon cable leading to the motherboard, the motherboard connector it goes to has 39 pins, I tried shorting all of them and nothing happened, am I trying it on the right thing do you think?
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by:PavPPZ1
ID: 24329647
I ask that because nobus's document shows only 10 pins on receiving end up the motherboard.
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by:nobus
ID: 24333505
you must remove the 20-pin connector, and short those pins on the mobo (the wires can be broken)
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by:PavPPZ1
ID: 24337256
I did remove the connector, but on the document you sent, it shows 10 pins on the motheboard end, on the motherboard there are 39
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by:nobus
ID: 24337737
i only drawed 10, but there are 39, as you can see on the picture next to it.
it is ONLY for showing the location!
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Author Comment

by:PavPPZ1
ID: 24337960
Ohhh, gotcha, so if I short the two right most pins it should turn on if the motherboard is okay?
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by:nobus
ID: 24342683
i don't thinkk so.
you have the small PCB with small cable (2 right pins there)
connects to      BIG PCB with large cable and this connects straight to the mobo
on the BIG PCB, i pointed out the switch pins are the one under and left of the missing pin; and the 3rd one.
is that more clear ?
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by:nobus
ID: 24342684
...to show which pins on the MOBO you can short
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by:PavPPZ1
ID: 24367888
Okay, I ordered the new motherboard, I'll let you know how it works out, thanks for all the suggestions so far!
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by:chilternPC
ID: 24368881
hopefully its not the CPU ? ;-o
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by:PavPPZ1
ID: 24369215
If it was just the CPU wouldn't it at least power up, fans come on or anything?
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by:chilternPC
ID: 24369714
as far as I know the CPU tells the motherbnoard what to do. without the CPU the motherboard is like a body wityhout a brain.....
having said that - it could  be the motherboard is dead and not the CPU. or it could be both or it could be the CPu. sorry.
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by:nobus
ID: 24371923
odds are 95% mobo, 5% cpu failure
so normally, it is the mobo
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by:PavPPZ1
ID: 24397078
So I replaced the MB and the same exact thing happens.
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by:chilternPC
ID: 24397550
what motherboard did you get? a dell replacement ?
I assume its got the same pin outs for the switch, power....capatible CPU....
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by:PavPPZ1
ID: 24397610
same exact motherboard that was in it
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by:nobus
ID: 24397642
then it looks like you hit the 5% ..
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by:PavPPZ1
ID: 24397655
shouldn't it at least power up even w/ a bad cpu though? generally the fans etc will at least come on, i'll try another one though
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by:PavPPZ1
ID: 24397689
It does the same thing w/ another processor as well.
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by:nobus
ID: 24397696
that would depend on the actual fault
an example : if you keep the reset button closed,  try booring, and see what happens...
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by:PavPPZ1
ID: 24397764
There is no reset button, and I don't know what you mean by "booring"
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by:nobus
ID: 24397783
booting
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Author Comment

by:PavPPZ1
ID: 24397828
oh, when you press the power button absolutely nothing at all happens, so i can't try booting
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by:jamietoner
ID: 24398091
I would replace the control panel(also called i/o panel), the i/o panel cable and the power button. I'd get the cable first(part# Y8227) as I've seen these get pinched and cause issues similar to yours, then the power button(part# J8995), then the i/o panel(part# f8912). These I think are much more likely to cause this issue than a bad cpu. These parts can be found on ebay(cheapest place), from impact computers(www.impactcomputers.com) and from Dell(usually expensive).
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Author Comment

by:PavPPZ1
ID: 24398153
So the motherboard was probably fine, its just these parts?
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by:jamietoner
ID: 24398211
Probably.
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by:PavPPZ1
ID: 24398290
Why would the audio/usb board need to be replaced?
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by:jamietoner
ID: 24398312
The power button connects to it, a short in it would cause the power button to not function.
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by:PavPPZ1
ID: 24399383
Any suggestions on which one I should start w/ to replace instead of having to buy them all?
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Accepted Solution

by:
chilternPC earned 500 total points
ID: 24400081
is the motherboard (both versions) seated correctly on the chassis ? have you tried a new power supply on the new motherboard - maybe the old motherboard shorted out any power supply and so when you changed the mobo  - no work  - as the power supply was stuffed by the last mobo.
just a thought. double check the earth and the power supply.
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by:nobus
ID: 24401516
i was answering to your question "shouldn't it at least power up even w/ a bad cpu though? generally the fans etc will at least come on"
and i said  (on a normal working pc) to hold the reset button , and try booting
then NOTHING happens, since the cpu is kept in a reset condition
and yes, i KNOW you can't boot
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Author Closing Comment

by:PavPPZ1
ID: 31578182
Thanks so much 100% right, I had tried another PSU before replacing the motherboard, not not after, tried another one after putting in the new MB and it came right on, thanks again!
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