Chosen Solution
Hey, a friend droped his phone and smashed the screen to pices, but it still worked, Few days later he dropped it again, from pretty short distance and it landed on top right corner. Phone stop turning on from this time. I tried opening the phone, reconnecting all the ribbons from screen part of the phone as well as battery. Following actions made no difference and the phone is still not recognizable in iTunes. What should be my next steps in troubleshooting? It may be difficult since i don’t have my multimeter yet.
At this point, you could try to disconnect the screen assembly (disconnect the battery first) and try connecting it to an iTunes enabled computer. If the phone is not recognized, then you probably have a logic board issue. This is much harder to troubleshoot and considering you don’t have a multimeter yet, it is probably beyond your skill level at this point in time. If you still want to proceed, then get your multimeter and then find the schematic online (sorry we can’t share them here) and find PP_BATT_VCC, PP_VCC_MAIN and PP5V0_USB. I would start by checking to see if those power rails are shorted to ground (device has battery disconnected). If one of these rails is shorted to ground, then you will need to identify what is causing the short. It could be a bad decoupling capacitor, conductive debris or defective IC that is directly supplied by those rails. If they are not shorted, then you can connect, preferably, a known-good battery to see what voltage you measure. If you are measuring the proper voltage, then you move onto the PMIC and check the voltage rails it generates. But that is pretty advanced and you should report back before going too far.
Is the battery seated/connected correctly? Have you tried plugging in the lightening cable and then tried power on
