I have a Lenovo Y470 on the bench. It runs off the battery till dead, has no power LED but power is present at mainboard from charger. So here are the existing conditions:
Charger is good
 19 volts +/- Present at mainboard
 No power led when plugged in
 Will not Power on
 Will run normally off charged battery until depleted
 Will not charge battery
 So it appears that there's something open between Power in at board and charge circuit. There are no apparent breaks on board and checked all fuses, power resistors, chokes and I don't see any burnt or damaged lans on board. Any help would be much appreciated. If there was only A SCHEMATIC OF POWER/CHARGE and DISTRIBUTION it would be a piece of cake for me.