* Power off
* Disconnect the power cable from the XPS 8700
* Remove the cover (page 15)
* Remove the front bezel (page 22)
* Remove the top cover (page 47)
* Trace the power button module cable (page 57) to the motherboard
* Reseat the cable
* Disconnect/reconnect every other cable connecting to the motherboard
* Reconnect the power cable to the XPS 8700
* Press the power button. What happens?
I removed the top cover and moved the push button around while pressing it. The PC powered on. I think the button module is faulty. It has to be pressed without the top cover a certain way for the power to come on. I found a replacement on eBay. Thank you!