Störungsphänomen
The SIM card cannot be recognized on the phone.
Störungsbeseitigung
First, we need to take apart the phone and run the cosmetic inspection of the motherboard. There is no water damage oder deformation.
Dann messen Sie die working voltage of the SIM card connector, the measured value pin of SIM_DETECT is 0.45V, which is abnormal (normal voltage value should be around 1.8V).
Aus dem Schaltplan, we can try to replace R202_E (100K) with a new one (1K).
After finish replacing the resistor, then assemble it, and test again, the problem resolved.
Tipps:
For the SIM card issue, like no SIM card. We need to focus on checking the related pins diode value and voltage values.
If there’s any abnormal, then refer to the block diagram or the schematics to check and find out the relevant components then get it replaced.
Here, in this case, the voltage on the SIM_DETECT should be around 1.8V. But the actually measured result is 0.45V only. So the possible reason is the resistor with a problem. So in order to introduce a proper voltage into the rail, we can try to change a very small resistor to have a try.
iPhone X Motherboard Reparatur Kurs
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