XPS 730x, Master Control Board reset jumper

there is a blue jumper on the MCB with small silkscreen instruction.

it goes:

1-2 reset to factory default

2-3 normal operation.

User who had the MCB setting messed up from previous Dell motherboard can use the jumper to reset all LEDs to default white color.

I am testing if user does not care about changing LED color and just leave it lit all white like a car front lights, and does not care about monitoring temperature or fan rpm, there is option to disconnect cable between MCB and motherboard, so the settings in MCB is crystalized.

that cable is connector 12

do not confuse it with connector 13, which should stay connected.  It is a relay of power button to motherboard power switch.  It receives power LED and HDD LED from motherboard to show up as power light LED and hdd led on front panel.