Ok summary:
Voltge measured accross componant
PR319 - 19V
PC264 - 19V ish
PC78 - 0v
C404 - 0v
C401 - 0v
C417 - 0V
C420 - 0v
This shows that my 5V and 3.3V rails are non existant right?
So you have VA and VA1 (i.e. PQ72,49,7 should be OK) but no LDO5 nor VDD3. I would then move to sheet 40 of the schematic where those voltages are generated by the buck converter UP6182 (incidentally, it looks to be a direct clone of the TPS51125, if you ever need to replace it - even the
datasheet looks like a copy-paste job).
Check voltages across these, they should be close to PU7 (the '6182):
PR91 (master enable pin for the LDOs) - part might not be installed, just check the pads
PC90 (LDO3, worth checking although nothing seems to use this rail)
PR118 (3V3 enable pin)
PR114 (5V enable pin)
After a bit more looking through the schematic and datasheets I have a better understanding of the power system: 3.3V buck regulator is enabled all the time and powers most of the standby circuitry (including the EC), while 5V and the others are controlled by the EC (look at signals DD_ON and USB_CHARGE_EN).