Fake charging - I give up :(
I have an iPhone 6 Plus that I’m battling with (and losing badly), that has a charging issue. The phone recognises the charger and shows the charging symbol, but the battery does not charge and battery % does not change. The amp meter shows quite an unstable amp reading constantly changing and ranging from 0.25amps to 0.6amps. When the screen goes to standby/inactive the reading drops to almost zero amps.
I have all the correct diode readings on the dock connecter. I get 3v on PP3V0 Tristar. When I connect a charger with no battery connected I get between 3.8v to 4.2v on PP_BATT_VCC. I’ve tried the board with a known good charging port and battery, unfortunately I still have the same issue.
I started with replacing Tristar/U1700 as I find this solves the issue in the vast majority of cases, however not this one sadly :(, I’ve also replaced Tigris/U1401 and Q1701, however I still have the same issue.
Here’s the interesting part, I decided to replace the MOSFET Q1403, before doing so I bridged PP_BATT_VCC & PP_VCC_MAIN (with Q1403 removed). This solved the problem, the battery charges normally and the amp meter shows a more constant 0.8amps whether the screen is active or not. I thought I’d cracked it at this point and replaced Q1403 with a new one (well from a donor board). Unfortunately the same issue came back with the replacement of Q1403.
I’m completely baffled now, any ideas anyone? I will be greatful of any thoughts as always :)