Zero watts described the result, not the cause
The initial meter showed no useful input and the screen remained black. Those observations justified following the USB power and detection path rather than identifying a component from the symptom alone.
PP_VAR_USB_RVP_R was missing
The absent rail mattered because Tigris U4000 is expected to produce the 5-volt supply passed toward the USB IC for cable-insertion detection. Without it, the downstream charging conversation could not begin normally.
Replacing U4000 restored the path
Tigris was replaced under magnification. During the retest, input power returned, the Apple logo appeared and the phone reached its lock screen.
Why another zero-watt phone still needs testing
A damaged port, interrupted connection, protection component or another controller can also prevent input. The missing rail was the decisive finding on this board.
