1. Is there an iCloud activation lock?
Especially important! It is recommended to confirm whether there is an iCloud activation lock on the iPhone through Apple official website. If there is an activation lock on the purchased second-hand iPhone, firstly, it is impossible to confirm whether the seller is the owner. Secondly, the iPhone may be directly locked remotely in the future, so it is not recommended to buy a second-hand iPhone with iCloud activation lock.
Second, the query serial number
Some important information of mobile phone serial number, such as activation time, remaining warranty period, etc. , which can be confirmed by third-party tools such as Apple official website or fruit powder query. Because the mobile phone case and mobile phone accessories of the second-hand iPhone may be forged, it is basically meaningless to compare several codes.
The serial number of iPhone is determined by the motherboard, but fraudsters in the market may tamper with the serial number, but checking the serial number can be said to be the first step of machine inspection. The serial numbers of table tops, Korean versions, Japanese versions and American versions often appear on the Internet have been changed to Bank of China. You can even write the serial number of the motherboard without iCloud lock. Once the brush machine is reactivated in the future, it will be locked again by the iCloud activation lock and cannot be activated.
As for how to identify whether the serial number has been tampered with, please read article 3 carefully.
Third, DFU brush machine
After getting the machine, it is recommended to use DFU mode to brush the machine thoroughly through iTunes. You will know if it is a demon machine.
DFU mode of iOS: develop FirmwareUpgrade, that is, the forced upgrade mode of iOS firmware. Please refer to other methods for specific operations.
If you buy all kinds of so-called "devil machines", the following may happen in the process of DFU recovery:
1. The error code cannot be recovered.
If there is an error code, you can first refer to Apple's official technical support document: get help on iOS update and recovery errors. If the above methods can't be reactivated, then this machine is probably a "demon machine".
2. It cannot be activated after brushing.
You can't activate the machine after brushing, or you have confirmed that there is no iCloud activation lock (refer to the first one) before brushing, but you are prompted to enter a strange Apple ID to activate, then this machine is probably a "demon machine" or a machine with a modified serial number. In addition, if the sticker machine or foreign contract machine is unlocked through illegal channels, it will not be activated normally after the brush machine is completed.
3. Being in the "white apple" interface for a long time during brushing can't continue the next step.
As long as the data cable connected to the computer is original, the connection is normal and uninterrupted, the computer network connection is normal and the operation steps are correct. If you repeatedly try to brush the DFU machine, only the Apple LOGO still appears, but you can't enter the next step for a long time, then this machine is likely to be a "demon machine".
Fourth, hardware detection.
Because you know in advance that you bought a second-hand mobile phone, you don't have to see if it smells of sandalwood or has a film on it when it arrives. First, judge whether the color, appearance and color of the machine are the same as those described in the picture.
Then start to check the hardware of the mobile phone, which needs to be tested one by one, which is time-consuming, and some details may be ignored.
Start testing all kinds of hardware to see if there are hands and burrs on the appearance of the mobile phone, whether the net cover of the receiver and speaker is woven net, and whether it feels as good as the genuine one. Then check whether the power button, volume button, mute button and HOME button are sensitive to touch, whether the feedback is obvious but not stiff, and check whether the camera has dust or cracks.
There are only a few items in the appearance part, then turn on the computer and go to the second stage.
Screen checking method: You can download some pure white, pure black, pure green and pure red wallpapers. The maximum brightness adjustment is to see if there is uneven backlight and bad light spots on the mobile phone, and the viewing angle is tilted to see if there is obvious light leakage at the edge.
* Whether the touch ID is normal: whether the fingerprint recognition function is input smoothly and whether the recognition is sensitive, just try to input it once and unlock it several times.
* Whether the mobile phone WIFI is normal: check whether the WIFI link is normal and stable, signal strength, etc.
* Whether the gyroscope is normal: Open the native compass program and try it.
* Is camera focusing available: you can try taking pictures, macro, etc. IPhone 6 has phase focusing, and you can also try whether the camera can automatically switch between short distance and long distance with the help of the palm of your hand.
* Whether the earphone is normal: whether the earphone is plugged in smoothly. If the headphone jack doesn't work, the motherboard may be damaged.
* Whether the distance sensor is normal: When making a phone call, test whether the receiver will fall off once the screen is covered, and whether it will be sensitive. Just try it.
* Whether the flash is normal: Turn on the camera to switch to the recording mode, and choose to turn on the flash. Pay attention to whether some models of cold and warm LED flash work normally at the same time, and you will know if you give it a try.
* Whether Bluetooth is normal: iPhone can only match other Bluetooth devices but cannot search other iPhones. Reconnect with a Bluetooth headset and try it.
* Whether the microphone is normal: open the voice memo program that comes with the system and you will know it as soon as you record it.
* Whether the vibration function is normal: tap the mute button on the side of the phone and try it.
* Is there a network lock: Turn off data roaming in cellular data, and you may not be able to access the Internet after turning off the built-in card pasting machine.
Note: If the application named "Qcard" must be a built-in card pasting machine.
* Whether to open it: You need to open it yourself to judge, mainly depending on whether the internal test paper is intact and whether there are obvious traces of motherboard maintenance or "flying line" welding.
* Accessories: This is particularly important. If the seller tells you that it is an original accessory, you can take a good look at whether the serial number in the power adapter is clear, whether the printed font is consistent with other original fonts, and whether the copper sheet of the data cable interface is neat, burr-free and corrosion-free. Apple's original configuration (data cable, power adapter, headphones) is still very expensive, leaving a lot of new business for profiteers. In addition, it is strongly recommended that you use the original accessories or accessories certified by Apple's official MFi, otherwise the motherboard may be damaged in the future, resulting in failure to charge or accelerate battery loss, leading to automatic shutdown and restart.