Really sounds like you need a new motherboard. since swapping the ps did not change the situation then that is the most likely source of your problem.
Dell spare parts or Ebay is best choice for a new motherboard. you cannot just put one in as dell system are proprietary
HomeBuilt SandyBridge P8P67 i7 2600k @ 4.5 ghz 8gigs GSkill Ripjaws. Corsair 800D Case and AX1200 Ps X-Fi Titanium Fatal1ty pro PCIe Sound CardDell Studio XPS 1645 Window 7 Pro
Forum member since 2003
1. I found this part number in another forum message. WM283
2. Are there diagnostic lights on the back of the machine? Usually there are lights marked 1 2 3 4 and they light up in a sequence to determine what is wrong.
ok so now we are at the either or situation..could be the powersupply or could be the motherboard...both of which can be very daunting to replace if you have never been inside a computer. If you don't fee comfortable then the options are either a friend or one of the big box stores repair either firedog or geeksquad. I am not sure how much they charge but i bet it is not cheap.
I am leaning more towards the motheboard as you do get the green light....can you also hear the fans and harddrives start to power up also and run for a few sec?. If you hear these sounds then the chances of the motherbord as bad increases..
The Power Supply (Dell or other ATX compatable) are easy to replace. However, need to check a few things first...
1) When you push the power button - do you NOT hear ANY fans at all?.. not even the PSU fan?
It could be a failed PSU, a burned out motherboard circuit or a short in the system wiring... the PSU/motherboard has a breaker that will keep it from powering on if there's a short - just lilke a circuit breaker to protect itself. If you've opened the computer alot - you need to check the wiring that powers the hard drives in the base of the case... I've heard of them getting cut/pinched by the case cover when you place it back on. There's two "sharp" clips on the bottom of the case cover that fit into slots - you could have accedently pinched/cut a wire. If you have had a shortout be warned, you've likely damaged a hard drive, the motherboard or cpu - but there's a chance they'll all be okay. If you find the damaged wire, simply repair it and try to reboot your computer.
2) If there's no short/pinched wires then you may have a bad PSU or power switch - especially if you don't get the BIOS boot screen that says "Dell" Usually if you have a bad motherboard, you'll at least get the PSU to power up with fan on, but just be staring at a black screen. If the BIOS screen comes on and it just fails to boot - you've got a bad HD.
3) If the PSU DOES power on, even for a second then powers off, you've either got the short or a bad motherboard- also easy to replace, just time consuming. YOU WILL need an XPS 400 replacement board if you hope to have it boot up and run like it originally did... otherwise, once you install a new (non XPS) motherboard, you'll need to re-install the OS on a new HD and mount the old HD(s) as additional drives to salvage any files you wanted to keep. You could just install the OS on the original drive, but you'll lose all your files.
Okay, so... if you think it's a PSU - all you need to do is:
1) unplug the computer and press the poweron button to discharge the motherboard (green light on MB will go off)
2) lay the computer on its side to access all the wiring harnesses and so you can unbolt the stock PSU without it dropping into the case.
3) un-plug all of your power connections (if you're unfamiliar with what plug goes where, make notes and mark the wires with tape)
4) unscrew the PSU -there's four screws on the back of the unit. There's also a spring-loaded clip you'll need to press inside the case to slide the old PSU out.
5) unscrew (there's only two) the heatsink casing covering the CPU (black hooded box with copper fins inside)- this will allow you to slide out the wiring that is tucked in behind. Once you remove the two screws, there's a swing hindge - the heatsink casing should just lift up like the hood on your car giving you access to the wiring.
6) pull out the old psu and wiring harnesses. - be careful not to damage the MB or any memory left in the slots.
Installation is the opposite
If you don't mind a small gap in the back, Fry's has an Antec 550w TruePower Trio for sale... $69 or, just google Dell PSU - there's several makers out there that sell replacement models that fit perfectly. Unless you have a hi-power gpu (something that takes an auxillary power PCIe plug, etc.) - just stick with a 350w - 400w replacement model.