The next problem is to find the physical location of the components on the board. Lickily all of the support components ahve only two pins, so the circuit was traced out using the following steps:
- disconnect battery, screen flat flex and frontlight flat flex
- with a multimeter in continuity/diode mode (i.e. using beeps) connect one probe to the chip pin of interest and locate the 'nearer' end of the first component by probing around. Note down the silkscreen component identifier.
- locate the next component(s) by probing the 'far' end of the found component and so on.
- probe around for extra connected components not shown on the diagram.
- also probe pins indirectly connected to DCDC1 and DCDC2 by external rails through wich current for the two subsystems might end up flowing.
After inspecting the relevant parts of the diagram we are only interested in a couple of diodes, a few capacitors and some inductors.
Inductors can burn out, so would fail open circuit.
Capacitors usually fail short circuit.
Diodes can fail short circuit or open circuit (aiui).
Measuring the component values in-circuit can give misleading results, so I just tested for open/short circuit.
I mention the above for the benefit of those who might think I know what I am doing.
I don't
