Tag: iphone won’t turn on

iPhone 12 Pro Max Won’t Turn On Issue Repair Guide
The iPhone 12 Pro Max, announced on October 13, 2020, is a high-end smartphone known for its advanced features. However, a serious drop can cause it to fail to turn on. This guide details the steps to troubleshoot and repair this issue.

Phone Details

Model: iPhone 12 Pro Max

Announced: 2020, October 13

Defect Phenomenon

An iPhone 12 Pro Max that has been seriously damaged by a drop may not turn on. In such cases, the following troubleshooting and repair process can be helpful.

Troubleshooting Process

First, let’s connect the motherboard with the DC power supply machine, there’s no current leakage. But when triggering the boot process by tweezer, the current jump to 1100mA directly.

Next, let’s remove the foams around the connectors, and then hold the motherboard on the heating platform to separate the two layers of the motherboard.

After separation, not surprisingly, a lot of pads have fallen off, later we need to take a lot of time to fix the missing pads. But anyway, let’s fix the boot issue first.

When measuring the diode values on the power rails which are outputted from PMU to CPU, find one capacitor around the CPU is shorted to the ground.

Refer to the Refox bitmap, it’s PP1V2_IO.

As we can see, there are many components related to the PP1V2_IO.

To find out the exact shorted component, we need to use the rosin inspection method.

Apply rosin smoke on the surface of the relative areas on the motherboard

Then connect the motherboard with the DC power supply machine and check under the microscope, we can find the shorted component easily.

Refer to the bitmap, it’s the capacitor C2941

Since it’s a filter-type capacitor, to avoid the potential heat damage to the NAND and connectors around it. We can just pick it off with tweezers directly.

After that, connect the logic board with the screen and boot with the DC power supply machine again, the phone can be booted.

Then, let’s fix the missing pads on the middle layer.

Fixing the missing pads is not very difficult but requires a lot of patience.

For the pad that has no connection point

We need to scratch out the root of the pad with a sculpture knife slightly first

After that, based on the “root” to jump wire and make a circle

Then solder a copper lug on the surface

Then cure and reinforce it with the UV mask and UV lamp.

Assemble and Test

Then assemble the two layers of the motherboard first with the heating platform

When the motherboard cooling down, assemble the phone to test and all the functions are OK.

The issue gets resolved by removing the damaged capacitor and recombining the two layers of the motherboard.

Summary

The iPhone 12 Pro Max issue of not turning on due to serious drop damage was resolved by:
- Removing the damaged capacitor (C2941).
- Recombining the two layers of the motherboard.
- Fixing the missing pads.
This repair requires careful inspection and precise work to ensure the phone is restored to full functionality without causing additional damage.
August 14, 2022
Fix iPhone XS Won’t Turn On with P12 (NAND Programmer for iPhone 6 – iPhone 11 Pro Max)

NAND replacement is a common repair procedure in iPhone repair, whether for storage upgrade or fixing issues like not turning on caused by a damaged NAND. For NAND replacement, a NAND programmer is needed to read and write the NAND data.

Today we will repair an iPhone with the latest NAND programmer P12, Compared to other NAND programmers on the market, P12 supports a wide array of models, which includes NAND read & write and WiFi unbinding for iPhone 6-iPhone 11 Pro Max and some iPad models. What’s more, P12 can work without an internet connection and is free for use permanently.

Then we use P12 to fix an iPhone XS that won’t turn on. The iPhone XS is unable to boot up.

Then we disassemble the phone for further testing. Connect the motherboard with Power Cable. The boot current only has 75 mA. It can be preliminarily judged that the system is faulty.

Next, connect the phone with the computer. The phone is in DFU mode automatically. The flashing gets stuck at 19%. We can confirm now that the not turning issue is induced by faulty circuits related to the NAND.

The next step is to replace the NAND with a new one. Remove the display and detach the motherboard. Apply high-temperature tape around the motherboard. First of all, remove black adhesive around the NAND with Hot Air Gun at 280 °C.

Pry up the NAND with Hot Air Gun at 400 °C.

Attach the NAND to P12. Please pay attention to aligning the NAND with the A1 pin. Click “Syscfg Backup”. Then save the data.

Remove the NAND. Attach the new NAND to P12. Select “User Backup”. Tap “Program”.

Next, we reball the NAND with the written data. Place the reballing stencil in position. Apply a layer of middle-temperature Solder Paste evenly. Heat with Hot Air Gun at 340 °C.

Before NAND soldering, we need to remove tin on the bonding pads. Apply some middle-temperature Solder Paste with Soldering Iron. Clean the bonding pads with Soldering Iron and Solder Wick.

Remove black adhesive on the bonding pads with Sculpture Knife. Then clean the bonding pads with PCB Cleaner. After cleaning, apply some Paste Flux

Align the new NAND. Heat with Hot Air Gun at 380 °C to solder.

Then we install the motherboard. Connect the phone with the computer to flash. The flashing has been successful.

The phone turns on normally. After activation, the phone also functions well.

October 15, 2021
Fix iPhone 7/7 Plus Won’t Turn On – CPU Repair

iPhone 7/7 Plus won’t turn on after it is dropped? Due to the imperfect technology of CPU supplier, the SDRAM of iPhone 7/7 Plus series can be easily damaged. Once dropped, the SDRAM might be short circuited and the phone won’t turn on afterwards. The traditional SDRAM replacing method is complex and easy to get it pseudo soldered. This time we introduced a new solution with CNC Chip Grinding Machine. Let’s check the video to see how we fix iPhone 7 plus won’t power on issue in a more efficient way.

September 10, 2021
Fix iPhone 12 Won’t Turn On By Infrared Thermal Imaging Camera

Today we will share a repair case of an iPhone 12 that won’t turn on. After multiple attempts to turn on the iPhone 12, the iPhone 12 still won’t turn on. We have excluded the possibility of the display assembly and battery faults, so we speculate the cause is the short circuit of the motherboard. To find the faulty part, we have used the latest infrared thermal imager camera that differs from the complicated rosin detecting. Let’s check it out!

May 26, 2021
How to Fix an iPhone 11 Pro Won’t Turn On

Having trouble with your iPhone 11 Pro refusing to turn on? Don’t worry, we’ve got your back! In this comprehensive guide, we’ll walk you through some practical and effective solutions to fix this frustrating issue.

Step 1: Disassemble and test

Remove the two pentalobe screws at the bottom edge and lift the screen.

After the screen is lifted, take the shielding covers off, disconnect the battery, and remove the screen.

Connect the motherboard with the Power Cable. The ammeter shows a large current of 3.1A.

Detach the motherboard and connect the motherboard with the Power Cable again. The ammeter still shows a large current of 3.1A.

It indicates that the large current has nothing to do with other flex cables. The fault is on the motherboard.

Step 2: Run diode mode measurement

Run diode mode measurement of pin 1 on the J7010 of the battery connector. The diode value is 0 which indicates that the main power supply circuit is shorted to the ground.

Since the circuit simultaneously supplies power for the logic board and signal board, we need to separate the motherboard to locate the fault.

Step 3: Motherboard separation

Remove foam on the motherboard. Then heat the back of the motherboard with Hot Air Gun at 240℃ to remove the shielding paper.

Put the motherboard on the Heating Platform. To make it easier to remove the logic board after separation, drive a screw on the logic board.

Set the temperature of the Heating Platform to 185℃.

Clamp the screw to remove the logic board when the temperature has risen to 185℃. Lastly, remove the signal board.

Step 4: Run diode mode measurement again

Run diode mode measurement of pin 286 on the signal board. The diode value is 0. It suggests that the main power supply of the signal board is shorted to the ground.

Measure pin 286 on the logic board. The diode value is 363 which means the logic board is normal.

Open the bitmap. We can see there are many associated components on the main power supply circuit.

Step 5: Rosin detecting to locate the fault

Next, we need to locate the faulty component with rosin detecting.Remove thermal grease with a Sculpture Knife. Then dip rosin with Soldering Iron at 365℃ and smoke rosin on the signal board.

Set the direct current supply to 4.1V. Connect the positive and negative anode of the direct current supply with multimeter probes. Connect the black probe to the ground and connect the red probe to pin 286 on the signal board. We can see rosin on C1200_K has melted. It indicates that the capacitor is damaged.

Step 6: Eliminate the fault and restore the motherboard

Then we heat the damaged capacitor with Hot Air Gun at 350℃ and remove it with tweezers.

Clean rosin on the signal board with PCB Cleaner. Run a second diode mode measurement. The diode value returns to a normal value of 327.

Smear rosin with Soldering Iron and solder wick at 365℃ to remove tin on the bonding pad. Clean the signal board with PCB Cleaner.

Remove tin and clean the logic board with the same method.Attach the signal board to the Reballing Platform and put the Reballing Stencil in position. To prevent the solder paste from flowing into the motherboard crevices, insert a metal plate. Apply a layer of low-temperature Solder Paste.

Remove the Reballing Stencil and put the signal board on the Heating Platform at 185℃ to heat. After the solder balls are formed, turn the power off and cool the motherboard for 5 minutes.

Apply some Paste Flux and align the logic board with the signal board. Keep heating on the Heating Platform at 185℃. When the temperature reaches 185℃, keep heating for 1 minute.This step is to ensure that the logic board and the signal board fit closely.

Step 7: Test and assemble

Connect the motherboard with the Power Cable and short to the ground of the J7700 pin 12. The boot current becomes normal.

Put the motherboard on the phone. Connect the flex cables, screen, and battery. Because the battery is dead, plug the charging cable and the phone turns on normally.

Conclusion

iPhone 11 Pro won’t turn on with a large current. We found that the main power supply was shorted to the ground through measuring the battery connector. The fault was found to be on the signal board after separation. Rosin detecting showed us that C1200_K was damaged. After removing C1200_K, the fault was cleared.

March 9, 2021