Tip & How-To about Miscellaneous
IPhone 6 displays black screen and DC power shows the current flows normally but a little higher than that of average working iPhones.
Teardown iPhone and measure the diode data of each pin of display screen interfaces. The data is normal. There is no output after measuring the display power supply ±5.7v voltage. Replace the display screen power chip U1505, but the same problem still shows up. Therefore, we conclude there is something wrong with the surrounding circuits' resistor-capacitor units. After carefully measurement we find capacitor C1554 is short circuit. The location of capacitor C1554 is shown in bitmap picture 2-3 and material object is shown in picture 2-4. Replace it, the ±5.7v voltage output is normal. Assemble motherboard and turn on iPhone, the screen displays normally. Trouble is removed.
That the voltage of capacitor C1554 is under 5.7v suggests the damage of Touch IC chip or low starting conditions.
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