Way for figure out iPhone 6 Wi-Fi issues

Fault Description: iPhone 6 Wi-Fi can't be turned on while displays grey.

Possibility Reason:  The Wifi IC happens something abnormal.

We have tested the Wi-Fi, it really doesn't work, so the ICs may happens what we have doubted like that.

For this problem, first we can replace the iPhone WIFI IC directly. After install the iPhone WIFI IC, turn on iPhone 6, but it stuck when it entering the Settings, so the problem isn't been solved. Next remove the iPhone WIFI IC and test several key point signals, we found the 14 pin doesn't has the resistance value. Now, we need to check iPhone CPU, it's complicated.

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There is no Bus reset signal, the normal is 1.8V, we are going to borrow it from another place, and there is a 1.8V beside it.

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It's useless if we directly connect it, so we need to find a resistor to pull it up. Put iPhone motherboard under the Stereo Zoom Microscope, and then remove a boot signal pull-up resistor 220K,

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Install the iPhone WIFI IC, and then turn on the iPhone to test, now the iPhone WIFI function can be used normally.

Solutions for iPhone 7 Wi-Fi issues

Fault Description: iPhone 7 Wi-Fi, bluetooth can't be opened.

Possibility Reason:  According to the customer said, he found there exist leakage. And we confirmed that, meanwhile we found the backlight happens something wrong.

Usually, we will judge the damage of general function module will lead to leakage and rapid power consumption. Since the Wifi function cannot be activated, it may be caused by the damage of iphone Wifi IC.

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First, disassemble the iphone,  use DC Power supply  to power on, indicates that the current is missing, trigger more than 100 jumps. Then open the motherboard with QUICK 861DW Hot Air Rework Station  we discover it is a water machine, but before that, the customer didn't tell us .

Observe the iPhone under stereo zoom microscope and see that there is corrosion next to the Wifi. Maybe this is where the fault lies.

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Clean corroded area with wash water, and remove corroded filter capacitor, then connected to DPS DC power supply, the current starts to jump from 100 hops. So the problem still exist. We check other places and found a small capacitor under the compass that was corroded and damaged. Use digital multimeter to measure the voltage, there is a short circuit condition. Is this the reason of error?

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Remove the capacitor directly, measure the resistance value with a digital multimeter, and the resistance value is normal. It is also right after power-on. Install the motherboard and test, Wifi can be turned on, and the compass is back to normal. So dark backlight is due to screen. Fault have been removed, this repair work is over!

Wiser mind for iPad 5 NAND Repair

While the customer said, the iPad happens error 40, at the same time, it can't be turned on. 

Usually we will check the circuit board, so it is necessary to disassemble it, check the iPad motherboard.

First step, we need to connect it with the DC Power Supply, trigger it to test the current, the current stuck in around 40mA. Connect iPad to the computer and DFU restore it, it reports error 40. After entering the restore mode, we found the SN can't be identified.

According to the error code, we judged that it's the problem of iPad Nand flash or the circuit of the iPad Nand flash. Disassemble the iPad 5, take out the iPad motherboard, we found the iPad Nand flash has the trace of disassembling. Measuring the 1.8 and 3.3V of the iPad Nand flash, both doesn't have the power supply.

Check iPad schematic diagram via WUXINJI Dongle, we can know that power supply for both sets of circuits is converted from U3850.

Because the iPad Nand flash was disassembled, so we suspected that the power supply tube was virtual welding. Re-install it, the power supply is back to normal, but the iPad still won't turn on.

Now we need to use Quick 861DW hot air reworks station to remove the iPad Nand flash, after remove the iPad Nand flash, we found some pins of the solder pad are missing.

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Refill the solder pad, installing the iPad Nand flash to the iPad motherboard. Assemble the iPad and test it, now the iPad is turning on smoothly, the repairs end!

Way for solve iPhone 6S turn on failure

Fault Description: iPhone 6S happens something wrong on phone motherboard which lead the turn on failure.

Possibility Reason: According to the customer said, he dropped his phone into pool accidentally, so we doubt there may happen a short circuit.

Then, let us start the repair procedure.

Dissemble iphone with iphone opening tool , we saw that the motherboard was flooded with water, we cleaned the water area thoroughly, it seems that CPU Upper also exist fault. After tested resistance and powered on, there is no short circuit. Connect the iphone motherboard to the DC power supply, we find the current value is about 240MA.

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Test PP-VCC-MIAN with a digital multimeter , exist phenomenon of short circuit, the resistance is small, only dozens of ohms. Observe carefully, we found that capacitor next to the WIFI chip was black seriously.

Use QUICK 861DW Hot Air Station (VC194) to remove the capacitor,  resistance is tested more than 100 ohms, and the current measured is also more than 100 mA. Due to the large water poured area, it was found that a capacitor on the iphone audio IC also became black seriously.

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After removing the capacitor, measure PP-VCC-MIAN, then insert the DC power supply again, the current become more than 30 mA. Test multiple power supply, there is no short circuit, connect to the power supply, we feel a slight heat. So fumigate rosin in the upper part. It was found that power supply portion was hotter than other parts. After removing the display power, the current returns to normal.

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After replacing the iphone power IC, the machine can be turned on smoothly, fault is removed, this fix work end successfully.

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How to fix iPhone X charging problems

Fault Description: iPhone X happens something wrong on charging because of the tortuous repair process.

Possibility Reason: we doubt there happens something on 20-pin HYDRA-CON-DETECT-CONN-L.

Actually, usually the schematic problems, we will use the Wuxinji Dongle to check it, compared with normal value,  Insert the iPhone tail plug flex cable  and connect to J6400's 47, 48 pin, get 5V input voltage PP-VBUS1-E75. Then we will get the answers we want.

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U3300 output PP--VBUS1-E75-RVP and sent to U6300 via R3360 again.

HYDRA-CON-DETECT-CONN-L changed the name to HYDRA-CON-DETECT-L via R6410.

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HYDRA-CON-DETECT-L send the G3 pin to multi-function electronic switch U6300. When the U6300 receives a low level signal is also used to identify the link of iphone charging cable.

U6300 receives 5V power supply, and being tested that when tail plug being accessed, it will feeds the information back to the CPU (U1000) through the UART data interface. After receiving the 5V, the USB control chip U3300 IC  will also feed back the information of external 5V to the CPU through an R3332. Now, iphone's battery turns to green and the lightning bolt appears.

When need charging, the U6300 sends an turn on signal HRDRO-TO-TIGRIS-VBUS1-VALID-L to U3300, then the U3300 works and starts charging.

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Now, we know the Schematic, next use Hantek Digital Oscilloscope  to measure U6300 signal HYDRA-CON-DETECT-CONN-L, we found it was normal. And use Fluke multimeter (VC712) to test 5V voltage PP-VBUS1-E75 is only 4.5V, we all felt surprise that the problem comes from this.  Detected abnormal 5V from U3300, U6300, so it can not be charged.

We thought it was a small problem before, guess the lowered resistance cause to the low voltage . However, after test, we found the 5V appears short circuit, but the secondary body value is normal about 1600.

Repair Thought : Since the voltage is reduced, the chip connected to this line must be pulled down. But there is just a U3300 on the line, so replace the U3300 and test the voltage again. Then change the Circuit component connected to the PP-VBUS1-E75-RVP that from the U3300, (U6200, DZ5900, U6300) is the same.

The original 5V voltage is still only 4.5V, we already have no patience，
put it aside. After one week, we take the motherboard and decided to repair again, check from the peripheral circuits of each connected chip, when test the TIGRIS-LDO on U3300, it is actually short-circuited. Its voltage is only connected to two capacitors.

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This voltage is the linear voltage used by the power supply chip. Replace the Capacitance , charge and turn on, everything is normal.


Remark: The chip is linearly used for its own usage after get 5V main power supply. This circuit is also often found in notebook. Because the chip is usually a linear regulator module inside, the output short circuit usually pulls down the input voltage.

How to solve iPhone 7P charging problems and sounds problem

Actually, i am so sorry for the delay updating, the company organized a training for stuff, of course contains me. So i have to stop updated articles. But it is fine, i back now, next days, i will share more wonderful articles with you guys.

Today, we will talk about iPhone 7P charging and sounds problem, according to our customers said, he dropped this phone accidentally from the balcony, then when he is ready to reopen it, the faults occurred here.

Anyway, we need to diagnostic and do our best to fix it.

Firstly, we need to solve the charge problem cause if the phone can't run normal, the next steps will be much complex.

Plug the iPhone lightning cable, we confirm the iPhone 7P is not charging. Connect iPhone 7P to the computer, the computer also can't identified the device. Now, we confirmed that iPhone 7P charge problem is caused by iPhone USB charge IC.

Remove the USB charge IC from the iPhone motherboard, use digital multimeter to measure the grounding resistance value of the solder point on the solder pad, we found the resistance value of the C3 is infinitely large, and this signal point is connected to the main audio IC via resistor R3104.

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There are 3 kinds of possibilities for this case: first one is the resistor R3104 is damaged; second is the iPhone motherboard is pins dropped or disconnection; third is the iPhone audio IC is damaged. Remove the iPhone main audio IC, the pins is dropped, and circuit line is disconnected. Soldering jumper wire in this point, and replace the iPhone big audio IC. Now measure the resistance value of the USB IC C3 pin, the data is 480, which is normal value.

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Now the charging current is 1.13A, the charge function is normal. Because of the iPhone audio IC pins dropped and disconnection, after soldering the pins and replace the iPhone main audio IC, the iPhone audio function is back to normal, now we need to fix iPhone camera problem. Observe the iPhone camera, we found that was badly deformed. Replace the new iPhone camera, and then install the iPhone 7P, now the iPhone camera function is back to normal. The iPhone 7P was perfectly repaired.

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Solutions for iPhone 6 mobile phone no sound issues

Fault Description: iPhone 6 happens no sound issue

Phenomenon Description:  When we turns on the ringtone option on the phone, it will be stuck. Turning on the recorder, recording item can be clicked, but no any sound can be recorded.

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Facing up to the case, the possibility of a small audio failure is greater. Removing the iphone motherboard, we observed that  the large audio and the small audio have been replaced. As the case revealed, the culprit possibility of the chip itself is very small. Removing the small audio by iphone opening pry tool, and testing the small pad ground value of the pad, finding that the small audio F6 foot resistance is infinite (normally around 400)

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This is the small audio I2S bus, to the big audio and CPU. If refer to the big audio, removing the big audio, if it cannot work, you can consider to change the big audio ic, test the pin connected with the small audio F6 foot, the value is normal, it seems that from here to install the jumper wire to the small audio is all right

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After installing the jumper wire, which is used to repair phone logic board, and assemble your phone. The sound is normal after testing, and the recorder can record normally. Now, the repair is done.