オリジナル投稿者： dadioh ,
This is solved. Turns out the WLED display driver chip was internally shorted to ground. That in turn blew the 2A fuse that fed the P channel FET that drives the power to the boost circuit. Replaced the LP8543 device and then the 2A fuse (tiny 0402 package) but still did not have a backlight. Started probing around and discovered that the enable pin for the LP8543 was low. They use a 300K / 100K resistor divider network to get the 3V enable. My 300K resistor was open. Replaced that and BOOM I have a backlight. And that missing device is a capacitor on the output of the boost. Considering the hours I put into this it hardly seems worth it but I rescued this board from the landfill anyways :-) Soooo there you have it.