I have XPS 9550 WITH LA-361P REV 2 / TRIPOD motherboard. System will not POST (no Dell splash). If you hit power on, power light will turn on for 4 seconds and will turn off. USB is accessed during those seconds. No function keys (F2 F12) do anything so system will not get into bios setup or diagnostics. Screen blank during this process. However, "D" key + power-on will go through graphic testing so screen is working and keyboard input is obviously working.

Suspected BIOS issue but after create USB bios disk, <ctrl><esc> power cord inserted will NOT result...

Re: Dell 9550 LA-C361P AAM00 Schematics needed

Did you ever have any luck on finding schematics? I have a Dell 9550 that is out of warranty by just a couple of month. System will briefly turn on but then turn off. Can not get past POST, no logo splash. Unable to get into Bios (F2) or diagnostics (F12). Could just be bios issue but already replaced battery. I would like to check voltages and see if there is any physical problems. I actually suspect a bios issue, visual inspection looks good. Would really like to see some schematics