The article describes the main problems of iphones and possible methods how to fix it.
1. The phone does not turn on or reboot. The first thing to look for is a faulty battery. Check battery and replace if necessary. Further, the system cable may be faulty. Another reason why the phone may not turn on is because the software has broken. Also, a malfunction of the power button flex cable can lead to such a breakdown, in this case it is necessary to replace the flex cable. A defective tristar and its replacement can resolve this problem. If the phone restarts, it is most likely a defective NAND Flash and it needs to be replaced. Also, a short circuit on the board or liquid getting into the phone can cause the phone to stop turning on.
2. The iphone does not charge or is quickly discharged. The charging and sync flex cable is either dirty or damaged. Sometimes the cables are damaged when removing the battery from the phone. The charging connector can be cleaned of dust and other contaminants with a dental probe. A malfunction of the charge control chip also causes the phone to not charge. To diagnose the operation of this chip, you can use a USB tester and a laboratory power supply. A software malfunction can lead to the iPhone not charging, in this case you need to make a Hard Reset (restart the phone). Another possible reason is a short circuit on the board, in which case the phone also heats up.
3. The phone does not see the network. To diagnose and verify the Baseband (modem) dial the test combination * # 06 #. With a working modem and modem power controller, the imei of the phone is displayed. To check the quality of cellular network reception and the operation of the radio unit as a whole, install a known-good SIM card with a positive balance and make a test call.
4. Wi-fi does not work. Immediately you need to determine whether it is “gray” Wi-Fi or just a weak signal. The “gray” Wi-Fi is most likely a result of a shock or a fall, then the contact between the chip responsible for Wi-Fi and Bluetooth and the phone’s motherboard is broken. There may also be another problem – the Wi-Fi chip is faulty. In this case, you need to replace the chip. How to identify a microcircuit problem at the diagnostic stage: go to the settings and look at the Wi-Fi switch, if the switch is not active, this is the “gray” Wi-Fi. Wi-Fi antennas can fail, for example, in the iPhone 6, this is a matching and mainboard antenna. In this case, it is enough to replace the antennas.
5. Touch ID does not work, this means the fingerprint scanner is not working. The reason may be: damage to the cable of the Home button or the Home button itself, improper connection of the button cable (via the circuit board cable) to the connector on the board. The amplifier may be faulty, for example, on the iPhone 7, this is a problem with the U10 chip. Touch ID may not work due to a communication failure on the I2C bus.
6. The display is defective. Symptoms: there are phantom clicks, stripes on the display or artifacts, the picture is dull or there is no picture at all. The first thing to do is reconnect the display. If after reconnecting the display module cable the malfunction remains, then replace the display.
7. GPS does not work. In this case, the phone’s compass shows incorrect values. A software failure may have occurred. You must turn GPS off and on again in your phone’s settings. To do this, in the iPhone you need to open Settings, then General, and Location Services. Reset network settings in Settings. Alternatively, you can turn on airplane mode for a short time.
8. There are no sounds on the phone. If during the verification it turned out that the interlocutor does not hear you, most likely the main microphone on your phone or the earpiece from the subscriber you are calling are malfunctioning. And if on the contrary, you do not hear the interlocutor, most likely the earpiece on your phone or the main microphone of the interlocutor is faulty. If all the microphones and the earpiece do not work on the phone at the same time, and the Voice Recorder application doesn’t work, this is a 99% faulty of audio codec located on the iPhone motherboard. In this case, you need to replace the audio codec.
9. The proximity sensor does not work. The purpose of the proximity sensor is to turn off the screen when you bring the phone to your ear during a call; to save battery power and to eliminate phantom clicks. It is located on the front camera flex cable. Repair consists of replacing the front-end flex cable. Sometimes the light transmittance of the display (copy AAA) is different from the light transmittance of the original display, and because of this, the sensor does not work correctly. In this case, a replacement display will be required. The power circuits of the proximity sensor may also be violated, in this case the phone motherboard needs repair.
In this article, we have considered the main faults of the phone, which are detected during the acceptance of the phone for repair. Short circuit detection, detection of faulty chips or radio components, as well as motherboard diagnostics are studied in detail on the course of bga soldering.