iPhone 13 reboots without service, Brother Chong teaches you how to analyze the fault and fix it
Have you ever encountered such a situation, your iPhone 13 suddenly has the problem of unreadable card or no service, or even restarts unexpectedly? Are you distressed and don't know what to do? Are you wondering what is causing this and how to fix it?
If you have such doubts, then you must read this article to the end, because today I am going to share with you a real case that teaches you how to quickly determine the problem with your phone and fix it with professional technical means.
This is a pink iPhone 13 sent by a fan from Kunming, Yunnan, who said that his phone was bought in a specialty store in February 2022, and the screen was broken after using it for about a month, and then he went to the after-sales service to replace it with an original screen, which cost thousands of dollars. But this time there was a more serious problem with the phone, that is, I couldn't read the card, and I don't know if it was the sequelae of the last fall. He heard that I was a professional mobile phone repair master, so he sent the phone to me, and asked me to help him check and record**, if you need to flash the phone, but also help him export the information and **.
After I received the phone, I first looked at the appearance and found that the phone had no obvious drop marks, and I couldn't tell that the screen had been replaced. I'll just turn it on to test it and see if the problem that fans said that the card can't be read is true.
After turning on the phone, I first went to About the machine, and saw the display screen prompt**Apple parts, indicating that the original accessories had indeed been replaced. Then I looked at the modem firmware version again, and found that there is, indicating that the baseband version can be read correctly. I entered the dialing interface again, typed *, and saw that the serial number could pop up. At this point, most of the groundwork is normal.
I just inserted the SIM card directly to try it, and it turned out that the card could be read, and the signal of China Mobile also came out, so I dialed ** to try it, and the result was normal. I thought to myself, can the phone's malfunction be automatically recovered? I communicated with the fan, and he said that there is another problem with the phone, that is, it will restart unexpectedly.
I went to Settings - Privacy - Analysis & Improvement and found files that started with panic, which are records of unexpected restarts. I clicked on one casually and took a look, and found that it recorded the time of restart, the model, and the reason for the restart. I found a file called panic string, which contains a detailed reboot log. I took a closer look and found that there is a word called busy timeout, which roughly means busy timeout. There is also a word called Apple Baseband, which is the meaning of baseband. From these two words, I can deduce that after the system fails to read the baseband information and times out, it issues a system reboot command, asks the system to reboot and record the restart log, and then reads it again.
I waited for a while and tried to dial ** again, but the result was that the call failed, and China Mobile in the upper left corner became unserviced. A few minutes later, the phone directly restarted unexpectedly. This confirms my judgment that the problem with the phone is with the baseband.
So if our mobile phone also happens to such an unexpected restart, how can we quickly determine the problem? Is this really the problem of judging faults based on restart logs? See here are my iron fans.,If you think this** is helpful to you.,I hope you double-click on the screen to send me a little heart.,You've worked hard.,Thank you.。 If you are also a user of Apple mobile phones, you must insist on seeing ** at the end today, I will post all the common daily restarts** What is the cause, you can take a screenshot and save it in case you need it.
Next, I want to show you how to use professional technical means to fix the baseband problem of this mobile phone. First of all, we are going to take apart the screen, we will first protect the face component, there are obvious fingerprint prints, indicating that fans often use Face ID. We first open the iron cover of the battery, disconnect the battery, and then disconnect the display, touch and sensor cables, and then we can remove the screen.
For baseband problems, signal problems without service, it is generally a motherboard problem. And iPhone 13 is a double-layer motherboard, responsible for the baseband and responsible for the signal, as well as the functions of the WiFi chip are on the lower layer. Due to the use of double-layer motherboards, the upper and lower layers are prone to problems when falling lightly or heavily. There is a hidden screw here, we cut all the screws, disconnect the cables, and we can remove the motherboard.
Take out the motherboard, we need to observe whether there are signs of cracking and deformation on the upper and lower motherboards. After observation, this motherboard has no traces of deformation and cracking, and it is very perfect and beautiful. Let's first add a power meter to the motherboard, press the power button, and see if there is any abnormality in the boot current. After testing, the boot current is normal.
Then the iPhone 13 is a double-layer motherboard, we need to separate the upper and lower layers to check the problem, tear off all the foam on the table, put the motherboard on a dedicated heating table to heat up, and use a heat gun to assist in heating. Until the weld joints of the upper and lower layers melt, we can separate the upper and lower layers. At this point, let's take a look at the solder joints that connect the upper and lower layers. After observation, there were no signs of falling at the welding points of the upper and lower layers.
Let's take a look at the lower layer separately, whether there are traces of cracking, this is all experience. This corner is prone to cracking, and there are no signs of service. We observed that there was no abnormality in the upper and lower motherboards, and fans had replaced the screen before, so we suspected that the soldering joints on the upper and lower layers may have traces of virtual soldering somewhere, so the failure came and went. The motherboard may be a little hotter or a little colder, and when the thermal expansion and contraction are cold, the solder points cannot be connected to the baseband, and the CPU will send a restart command.
We need to treat the welds of the upper and lower layers to make them stronger. Let's first coat the solder joints on the upper layer with flux, smooth out each dot, and then clean them to observe. After the weld points of the upper layer are processed, we will deal with the weld points of the lower layer. Let's take a closer look, the baseband chip is Qualcomm's X60 baseband, and next to it is the wifi chip. Both chips are encrypted, and one mobile phone corresponds to the other, and once damaged, it cannot be replaced. This is the power supply chip of the baseband, below this is the intermediate frequency, and next to it is the power amplifier. Some people have always asked, what is the chip that is air-soldered here? It is a millimeter-wave chip only available in the American version, and the Bank of China is non-soldering and useless.
We dragged the lower motherboard with a welder, and the tin was smoothed out like the upper layer. So there are all kinds of mobile phone restart records, what is the reason for your mobile phone restart? Be sure to stick to the end of the last**, and I will post a common restart** for you to analyze. Finally, clean it up and observe it. The lower layer is then placed in a dedicated direct suction platform, and a new suction ball is implanted into the lower layer of the welded points of the upper and lower layers. Apply solder paste, scrub clean, heat and blow to melt each tin spot. After the processing is completed, the lower layer is placed on the heating table, the flux is inserted, the upper layer of the A15 CPU is coated with thermal silicone grease, and the upper and lower layers are laminated. Note that when we touch the upper layer, it will have the effect of QQ bounce rebound, indicating that all the tin dots are melted and soldered.
At this time, quickly cool down the motherboard, complete the soldering, clean up and down the left and right sides of the motherboard, add the power meter, and see if there is any abnormality in the soldering. OK, the start-up and start-up currents are normal, continue to put back all the foam and stickers to the motherboard. After the motherboard is beautified, clean the screen, put the motherboard back on, and buckle all the connecting cables. Attach a large screw that holds the motherboard in place. Then clean the area around the screen from any adhesive residue.
So is the restart pointed to by the restart ** necessarily caused by this problem? Here's what I want to tell you, not necessarily. The so-called reboot analysis can only be used for reference, not all trusted. Different phones show the same restart**, but the fault is not one. The so-called reboot** is also the main thing to help you analyze the problem, but it is not 100% certain, and it is the problem here. In addition to the questions indicated, experience is also very important.
We put the screen back in and put all the screws in place. Finally, do a cleaning process, tear off the protective sticker of the waterproof glue, and tear off the protective sticker on the **. Then close the screen and we place the phone in the packing tool to hold the pressure. After the pressure is successfully maintained, take out the phone and put on the two screws at the end. Use this to see the data cable on the power bank to turn on the phone. After turning on the phone, we enter the password of the fan, the welding of the upper and lower layers, and we mainly check the wifi and baseband.
Here it prompts that there is a problem with Face ID, so don't worry, about this machine will also prompt that there is a problem with Face ID. It's still the 128G National iPhone 13. The Wi-Fi address and modem firmware, as well as* are all normal. At this time, we still have to insert the card to test it. Hello, then you go to trial. Dialing ** and wifi function is normal, indicating that the upper and lower layers are welded very perfectly. The reason for the prompt that there is a problem with Face ID is because after our single motherboard is powered on and turned on, it does not have external support, so it will prompt that Face ID is not available. Let's enter the face once, and then look at it, and there will be no prompt that the face ID is not available.