Repairing SK hynix eMMC “Bad Health” Using F64 Box (Guide 2025)

Repairing SK hynix eMMC “Bad Health” Using F64 Box – Easy Explanation

In mobile phone repair work, one of the biggest problems is eMMC damage. Many phones become dead not because of software, but because the internal storage chip gets weak or damaged. This problem is very common in older phones and heavily used devices.

In this article, we explain a real repair case where an SK hynix eMMC chip with bad health was repaired using the F64 Box. The phone used in this case was an Oppo A1 (CPH2083). The good thing about this method is that it fixes the chip without permanent partition limits, which older tools could not do.

Everything is explained in simple words so anyone can understand the process.

Understanding the Main Problem

When an eMMC chip starts failing, it usually shows Bad Health. This means the storage has been used too much or internal errors have developed over time.

In this case, the phone was completely dead. When the eMMC was checked, it showed serious problems.

The health report showed:

• SLC: Not Defined
• MLC: 80% to 90% life used
• Phone status: Dead

“Not Defined” means the chip controller cannot correctly read some internal data. This is a very bad sign and normal flashing tools cannot fix this issue.

Why Normal Tools Fail in Such Cases

Most old repair tools fix eMMC problems by permanent partitioning. Once partitioned, the chip cannot be reused properly again. This also reduces the chip life and limits future repair options.

Because of this, many SK hynix chips were considered one-time repair only. After that, they were useless.

This is where the F64 Box becomes very important.

Step 1: Hardware Connection

The first step is hardware-level work.

The damaged eMMC chip is removed from the phone motherboard carefully. After removal, the chip is reballed so it can be connected again properly.

Next, the chip is placed into the BG 254 socket of the F64 Box. Once connected, the F64 software is opened on the computer.

At this stage, the tool detects the chip.

Step 2: Initial eMMC Diagnosis

After detection, the F64 Box scans the chip.

The chip details show:

• Brand: SK hynix
• Model: HB8AP
• Manufacturing year: 2020
• Capacity: 32 GB

The health report again confirms the problem:

• SLC is not defined
• MLC health is almost finished

This confirms that the eMMC is badly degraded.

Step 3: Choosing the Correct Repair Files

The F64 Box uses special files called FFV files. These files are made to fix internal controller issues of eMMC chips.

In this repair process, two important files are selected:

• Final HR
• Patch Final

These files are designed specifically for health repair, not normal flashing.

Step 4: Writing the FFV File

Now the main repair process begins.

The Final HR file is selected and written to the chip using the F64 Box. This process does not create permanent partitions. Instead, it resets internal health data inside the chip controller.

This step fixes hidden errors inside the eMMC.

The process takes some time. During this step, the chip should not be disconnected.

Step 5: Checking the Health After Repair

After the writing process is complete, the chip is removed and connected again to the F64 Box for checking.

Now the health status shows a big improvement:

• SLC: 0% to 10% life used
• MLC: 0% to 10% life used

This means the chip health has been restored close to factory condition.

At this point, the chip is no longer dead and can be reused.

Cross-Checking with Easy JTAG Box

To make sure the repair is real and not just a false report, the chip is tested again using another professional tool called Easy JTAG Plus Box.

First, the voltage is set to 1.8V, which is safe and suitable for SK hynix chips.

Then a Smart Report is generated.

The report confirms:

• Health is truly restored to 0–10%
• Partition Setting shows 0x0

This is very important.
0x0 means no permanent partitioning has been done.

So the repair is clean and safe.

Why This Method Is Very Important

Earlier, many SK hynix chips could only be repaired once. After partitioning, they became limited forever.

With the F64 Box:

• No permanent partition is created
• Chip life is preserved
• Chip can be reused normally
• Dead phones can be revived safely

This is a big improvement for mobile repair technicians.

When This Repair Method Is Useful

This method is useful when:

• Phone is completely dead
• eMMC shows bad health
• eMMC shows “Not Defined”
• Normal flashing tools fail
• Storage error blocks boot

It is mainly used by professional technicians, not normal users.

Important Warnings

This process is hardware-level repair.

If done wrongly:

• Chip can be damaged permanently
• Data may be lost forever
• Phone may never boot again

Always make sure:

• Correct socket is used
• Correct FFV files are selected
• Voltage is set properly

This method should be done only by experienced people.