We've received an iPhone 8 Plus from our
customer, the problem is that the iPhone 8P dropped before, and then the iPhone
8P is no service after insert the SIM card, if we don't insert the SIM card,
the iPhone always prompts "no SIM card Installed".
For a dropped iPhone, mostly the iPhone
solder pad pins are missing, or the iPhone is short-circuited by dropping. The
iPhone 8 plus was dropped before, so we suspect that the solder pads are off
the pins.
After disassemble the iPhone by phone opening tools, we found the
iPhone has been repaired by other repair man, the DSM_LB_E and DSM_HB_E chips
on the iPhone motherboard had been removed.
Use Fluke 15B+
Digital Multimeter to measure the diode data for iPhone
solder pad, we found the SCLK_HB_LB_DSM_FILT_E signal for the DSM_LB_E and
DSM_HB_E IC is short-circuited.
Open the WUXINJI
Dongle to check iPhone schematic diagram and
bitmap, we found the previous repair man installed the R1608_E resistor in the
C1602_E capacitor position, the position of the C1602_E capacitance on the
schematic diagram is not installed.
Use tweezers to remove the resistance on
the C1602_E capacitor position, and then use QUICK
861DW to solder it to the original place, solder
the jumper wire to the missing pins on the solder pad, and welded the component
chips. Now install the iPhone and test it, but the problem still there.
Disassemble the iPhone, observe the iPhone
motherboard under the 3D Digital Microscope, comparing with the iPhone schematic
diagram, we found the FL1501_E inductance missing, but it's installed on the
schematics diagram.
Connect the missing inductor directly,and then
turn on the iPhone to test.
Now the signal is normal after insert the
SIM card, and the phone call is normal, the repairs end.
This failure is caused by missing pins on
solder pad and dropped components.




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