when I got my Lunar-51, the guy told me the top power button board was 'iffy', so he sent me a new one along, left it to me to figure it out. Sure enough, the pc would die quickly w/that top power-on board, but the new replacement cured it. On eBay they are most often called the top i/o:

• http://www.ebay.com/itm/Dell-Alienware-Area-51-Area-51-ALX-Top-I-O-Panel-Assembly-MP-00005013-000-/251636978307?pt=LH_DefaultDomain_0&hash=item3a96bb9283
• if you're stumped, look into the method below to test your top pwr on switch board
• the diodes resistors switch can go bad, that's a fact

• 'Alienware A51 ALX no longer turning on':
• http://en.community.dell.com/owners-club/alienware/f/3746/p/19594844/20663918#20663918

You'd basically back your lower right 'panel header' connector off, read the fine text at the header, find which two wires are for the power on switch (up top), use a needle to back those pins/wires out, re-attach the panel connector, insert a paperclip etc into the slots where the power on wire-pins were. The top power switch is a 'momentary switch', which means you only need to pop your paperclip in long enough to make a contact - turn the pc on - then qwikly back it out of there. Shut down would be through Windows.

the black 5x5 connector is labeled FP1: Front Panel (Header) 1

lift up w/a needle on the soft black plastic retainer 'arms' to back the blk/tan pins out, then jump-start pc on, see what happens ...

If your system (& your top power-on board) is now 'ok', your system should run w/out a shutdown issue, & indicate you need a new top i/o (a new power on switch board).

If your system shuts down, your top i/o might be ok, & the problem is elsewhere. Another opinion is that some other part of the top power-on board has failed, a condition I assume happened to mine too.

this board looks exactly like a good one, but it is 'bad' for some strange reason ... see below for info

Thank you for the information!

I edited in new info to consolidate, best to find what's new up there. Report back? I think we can trouble-shoot your problem, get you back in b'ness.

Ok, I got to thinking & I'm no expert @ this. When the motherboard is turned on using the top power on button:

• the power supply turns 'on'
• the master i/o board now goes hot over the 10pin when the psu goes hot

However, the top i/o 'power-on board' as I call it, plugs into the master i/o board also. Whether or not being plugged in helps form a 'feedback loop' for the master i/o board (& all of its ic's) to 'wake up', IDK.

I've asked you to back your blk/tan pins out of your 'panel header' connector - remove your top pwr on switch wire/pins from the system - then paper-clip 'jump' your mthrbrd on. However, my old top pwr on board is 'bad' yet the actual switch itself tests 'good'. Odd. Therefore I deduced a component on the board (diode/resistor what-ev) is bad. If that be the case, on hind-sight, simply jumping your pc on as I said to may not 'cure' this shut down issue (if your top pwr-on board is bad like mine was).

As I stated, if worse comes to worse, pay $20 (or less) for a spare top i/o. When it gets there, you would unplug your panel header:

• the 5x5 connector, lower right of mthrbrd 
• labeled FP1: houses the power-on switch, hdd led, pwr on led wires/pins
• next, unplug the connector from your master i/o board labeled: JFL1

Now, you'd plug in the new top i/o FP1 into your mthrbrd header & JFL1 into your mio. Simply press the power on switch and see what happens. That's a test situation that requires no removal or disassembly of your system: you simply patch a test part into your system. Got it? I write this in the event the simple 'paper-clip your mthrbrd on' does not 'cure' the shut-down issue. If not, look into a new spare top i/o in pursuit of a good testing top power-on switch board. Whew!

FP1 is the MthrBrd Front Panel Header side of this board: it includes the power-on switch, hdd led & pwr on led wires found in the 5x5 black connector going to/from the mthrbrd lower right 'panel header' I showed you.

JFL1 is an unknown aspect of the board, short of it probably 'tells' the master i/o board to 'wake up'. If the FP1 part of the board is ok, but the JFL1 part malfunctioned, the paper-clip test I described may be a dead-end. IDK. That's why a new test board might be the real 'cure'. Huh? I'd probably be where you are tonight had I not had a new board to trouble-shoot with. Were you to get a new spare like above, simply reach in & unplug your current FP1 & JFL1, then plug in the new spare FP1/JFL1, click the switch on & in moments 'shotgun troubleshoot' if that's the reason your system shuts off. I had the same problem, so I outlined a possible reason & possible cure here for you. Spare parts are a good thing to have when we can get them as cheap as we can these days.

I din't puzzle over my shut-down issue for hours; I was back up & running in moments & din't put too much thought into the why of it. Tonight I have though. Paper-clip 'jump' your mthrbrd on is a procedure I'd have used had I not a good spare on hand. It will be up to you to confirm if it 'works or not'. If not, try a new top pwr switch board in the event JFL1 aspect is 'bad'. Good luck, hopefully this is what's wrong.