Chosen Solution
Hi, So I have an iPhone 7 boot looping (boots, shows apple logo for about 40 seconds, apple logo disappears for a second and repeats this process until battery is drained. Charging the dead battery at around 5.2V, 0.6A. This value stays the same while boot looping until at some point it discontinues charging until the battery is drained and the process starts anew. I tried DFU and restore mode, both unable to connect to iTunes while other phones do. Tried connecting a different dock, battery, screen, disconnecting the front flex to no avail. It must be the logic board being faulty. But where? I am just starting out microsoldering. The phone is mine and has no sensitive data on it. So I really do not care if the phone will be dead when learning (as a matter of fact, I do, because that would mean I fixed the phone, but hopefully you catch my drift). I have not done any visual inspection or measurements yet. Hope you could give me some pointers as to where I should be looking at. Could this be tristar although the phone charges up to a certain point? I have water damage red spot at the logic board, not on the screen. No rust or corrosion of any kind though, the board looks brand new.
I suggest you invest in a good multimeter and DCPS. The DT-880 is very limited on its uses as sometimes you have to inject voltage into the board to find a shorted component. You will also need to purchase some needle point probes and an original power squid or an iPower pro. I prefer using the squids as they show true low amperage. The first rule in board repair is: To completely rule out parts. In the newer phones this will mean putting the logic board into a known good housing. With the older boards you can remove the board from its housing and connect known good screen, battery and dock connector. That is what I would do with the 7 series. The second rule is: Do not create variables with your repair. In other words do not start removing components from the board until you are sure they are faulty. For this repair I would rule out a prior audio IC repair as this can damage the baseband CPU and produce these symptoms. If no prior repair has been done you will need to diode some lines and compare to another known good board or ZXW. · PP_VDD_MAIN · PP_BATT_VCC · PP3V0_NAND · PP0V9_NAND · PP1V8 · PP1V8_SDRAM If all those lines are good I would consider replacing Tristar first as your phone should be recognised in DFU mode by iTunes if all the above circuits are good. If you had a Tristar tester it would be the first thing you would use. The next component I would look at would be Tigris. Remember to test the phone every time after replacing a component.
Hello Bart!I can see you are having a logic board problem. It might be that one of the logic board’s components have failed/need replacing. It might be with a component. Have you tested the logic board from a donor phone? Soldering would damage it if it has failed. Try and see if you can switch boards.Regards,RivRob
