Follow this guide to repair iPhone 6 black screen problem after dropped. This guide offers you a very detailed logic board repairs solution to deal with the problems that the black screen occurred on iPhone 6 after phone dropped. Let’s find out the faults together now.
Example of iPhone 6 Black Screen:
There was no display after power on the iPhone 6; Connected with the power, there was high current.
iPhone 6 Black Screen After Dropped Failure Phenomenon:
The iPhone 6 had been dropped into the ground and then the black screen occurred. After connecting with the power, the adjustable power supply showed high current, which meant there was short-circuit, the physical iPhone 6 with black screen problem is shown in Pic 6-74. See what it is like after dropped.
Pic 6-74 iPhone 6 after dropped
iPhone 6 Black Screen After Dropped Maintenance Procedures:
After disassembling the iPhone 6 and connecting the power with the board, the current of the adjustable power supply was about 1.7A, which meant it was still short-circuited. The supply voltage of the adjustable power supply was pulled down to 3.4V. The whole motherboard was heating up, especially, the power chip was the most serious part.
After the power was cut off, use a multimeter to measure the power supply on the motherboard, and it was found that the PP3 VO NAND power supply of the NAND flash was short-circuited with ground impedance value at 0. The measurement points of the PP3 VO NAND supply are shown in Pic 6-75.
Pic 6-75 The measurement points of the PP3 VO NAND in the bitmap
The capacitance indicated by the arrow can also be measured according to the preference in Pic 6-76.
Pic 6-76 The measurement points of the 3v power supply on NAND flash
This 3v voltage was connected in parallel with a lot of capacitors, and it will waste a lot of time and be inefficient to remove them one by one, therefore, I used directly the “burn-in method” to find the short-circuit point. The so-called “burn-in method” was to first use a soldering iron to smoke the board with rosin, then adjusted the adjustable power supply voltage to 3V, and adjusted the current limit to the minimum.
The output of the adjustable power supply was connected to the ground by the negative pole and connected to the short-circuit point by the positive pole. Then, the current knob of the adjustable power supply was slowly adjusted to gradually increase the current limit. By observing the position of rosin smoked on the board, the place where the rosin melted fast was generally problematic.
Smoked the capacitor which connected to the PP3 VO NAND with rosin by a soldering iron and then slowly increased current with the adjustable power supply. When increased to 3A, it was found that the rosin on the capacitor C0634 was melted, which can be judged that the capacitor was short-circuited, then power off the iPhone 6 and remove this capacitor directly, as shown in Pic 6-77.
Pic 6-77 Position of the removed capacitor
After removing this capacitor and connecting the adjustable power supply, there was no longer a large short-circuit, the current is normal, and it is successfully to enter the system. Removed a capacitor in the same position from a material board to replace it on defective iPhone 6. The problem had been fixed.
评论
发表评论