It had a short on the main vcc, but that dissapeared with 0.5a 3.8v of power (did not expect that it had a short) and also on pp_5v7 and 6v. I removed the U1501 ic, now there is no short on these lines, and I can messure voltages on for example the 1.8v. I’m stuck now, what to messure next? The board looks fine, it had some minor damage around the backlight diode that cleaned up nicely, but I expect the phone to power up first.
Will the iPhone power without u1501 on the board at all? And where to check next. Help is appreciated