Chosen Solution
Hello, I got a iphone 6 in that worked fined except for touch issues. Each time the touch came unresponsive, i only had to twist the phone a little and it worked again so i figured it would be the touch ic. I’ve replaced many touch ic’s already it not had a problem afterwards but this time the phone is dead. Like completely dead. I only conected a new charging port, a new screen and a new battery and plugged it in but it doesn’t get hot or use any amps at all. I replaced the ic once more in case it would have a short or something but still the same thing. Any ideas where to look for?
Start by checking the power rails (PN5V7_SAGE_AVDDN / PP5V7_SAGE_AVDDH / PP1V8) that supply the Meson IC to see if there are any shorts. While you’re at it, check the rails for the Cumulus IC as well (PP5V1_GRAPE_VDDH / PP1V8_GRAPE). If that looks good, then you can boot the phone without the MESON IC (U2402/the black one). If the issue is with the IC (was it reballed or replaced?), it should boot fine but will not have touch. If none of this works, then the problem can be anywhere. Check the main voltage rails (check PP_BATT_VCC & PP_VCC_MAIN)and work your way from there. The risk of any BGA repair is applying too much heat. When that happens, you can get solder ball explosions from underfilled IC’s in the area.
Sounds like something you’d have to look and understand the board schematics of. Sadly I’m not enough of an expert in that area, but think people like Louis Rossmann would be. That way you can use a voltmeter to figure out what is receiving power, how much power, and how much it should be receiving. But this would be more difficult considering no power is going in at all, by which point I would suggest doing some continuity testing to make sure things like the battery and charging port are even connecting properly.
