iPad Air 2 Shows High Current When Power On And Motherboard Chip is Hot

We can come across many issue of cellphone, we can fix some minor problems by myself, but we can fix it by repairman sometimes when it is serious. Today I will introduce the solution for iPad Air 2 shows high current when power on and motherboard chip is hot. Wish it is helpful for you. Most cellphone repair guide you can find in vipprogrammer.com.
Trouble Phenomenon:
When testing with display, DC power shows high current and power management chip is hot. This iPad Air has been fixed once.. After teardown, we find battery and LCD flat cable are stuck with insulating tape.
1. When we teardown motherboard, measure the diode data of the battery power supply pin and of PP_VCC_MAIN voltage. We can find the data is normal.
2. Then we connecte adjustable power supply to test and use tweezers to short connect power on pin. DC power displays the current changes and iPad can be turned on normally.
3. The third we can connect display screen to do further test and short connect power on pin. And find DC power displays the current changes normally, but the current suddenly rises when display screen is about to be bright. At the same time, we find the power management chip is hot.
4. The fourth we need immediately remove display screen and assemble it to a fine motherboard. And it displays normally. Therefore, we conclude the problem happens on motherboard. Measure motherboard display screen interface and find the diode data of the pins of backlight power supply PPLED?_BACK_REG_A and PPLED?_BACK_REG_B is infinite. We can be sure that the backlight circuit is open.


5. The fifth we measure the power supply inductor L4680 and L4685 near the interface and they are normal.


6. Finally we measure two diodes D8428 and D8458 connected with the above inductors (in below picture). They are burnt out, as shown in below picture Replace the two diodes and connect the display screen to test. The screen displays normally. Trouble is removed.