If the system won't POST with just the RAM installed (no battery, no SSD) -- then yes, the system board is faulty and would need replacement. You're looking at just under $400 to over $600 for a replacement board, plus labor, depending on the CPU and GPU on the board.  
Dear Members of the Dell Forum, My Dell XPS 15 9570 continuously restarts with a black screen and might be stuck in a boot loop. Problem description:- laptop starts itself automatically as soon as DC plug is connected (I disconnected battery to rule it out as potential error)- fans spin up, keyboard lights up, diagnosis LED below track-pad lights up in solid white, not flashing ...no code and no amber color- after 7 seconds fans stop spinning, LEDs gos dark for a very brief moment... and the cycle starts again... fans, Keyboard & diagnosis LED solid white, etc... The diagnosis LED stays white WITHOUT any flashing during the whole 7 seconds- during restarts no display output (also not via HDMI) What I tried:- disconnected everything to rule out any errors (battery, SSD, keyboard, power button, track-pad, all plugs on the mainboard but not the DC one and the fans, i even tried without RAM)- as soon as DC jack is plugged in, fans spin up and stop every 7 seconds (...to start again for 7 sec)- I also disconnected the CMOS battery for a minute or so and reconnected it, didn't help Question:Is the mainboard dead? Does anybody know this issue/what is broken, can I test anything else or do I need to buy a new computer? Thank you for your time and help! Thomas
XPS 15 9570 black sceen, no error code (solid white LED), 7sek boot loop