What This Error Means
The “SD Card Error” — also experienced as “Boot Failure,” the miner showing a red status LED on power-up, the miner not completing its boot sequence, or being unable to access the web interface after powering on — means the control board cannot read the firmware from its onboard storage or SD card. The miner’s operating system, firmware, and configuration are stored on either a built-in NAND flash chip or an external microSD card (depending on the model). When this storage is corrupted or unreadable, the miner cannot boot.
This is a relatively common issue that can range from a simple SD card failure to a more serious NAND flash corruption on the control board. The good news is that SD card-based models can often be recovered at home with a replacement card and fresh firmware image. NAND-based models require a firmware recovery procedure or, in some cases, NAND chip replacement.
Common Causes
- Corrupted firmware image — A power interruption during a firmware update, a corrupted firmware download, or a failed write process has left the boot image in an unreadable state. This is the most common cause.
- Worn or failed SD card — MicroSD cards have a limited number of write cycles. ASIC miners write log data frequently, and low-quality SD cards can wear out within 1-2 years of continuous operation.
- Damaged SD card slot — The microSD card slot on the control board has a broken contact, bent pin, or corroded connection that prevents reliable card reading.
- NAND flash failure — On models with built-in NAND storage (no external SD card), the NAND chip itself has degraded beyond error correction capability.
- Power surge during boot — A voltage spike during the boot process can corrupt the data being read from storage, preventing successful boot.
- Incompatible firmware — A firmware image for the wrong model variant was flashed, and the bootloader cannot execute it.
Step-by-Step Fix
Step 1: Determine Your Model’s Storage Type
Check whether your Antminer model uses an external microSD card or internal NAND flash. Older models (S9, T9, L3+) typically use microSD cards. Newer models (S17+, S19 series) use internal NAND flash but support SD card recovery. Look at the control board — if there is an accessible microSD card slot, your model supports SD card recovery.
Step 2: Check the SD Card (If Applicable)
Power off the miner. Remove the microSD card from the control board. Inspect it for physical damage. Insert it into a computer using an SD card reader. If the computer cannot read the card, the card has failed — replace it. If the card is readable, check if the firmware files are intact. Even if files are present, corruption may not be visible — a fresh flash is recommended regardless.
Step 3: Prepare a Recovery SD Card
Download the correct recovery firmware image for your exact miner model and hardware version from the Bitmain support site or a trusted source. The hardware version is usually printed on the control board (e.g., “BB V1.2” or “C55”). Using the wrong hardware version image can further brick the miner. Write the firmware image to a fresh microSD card using:
- Etcher (balenaEtcher) — recommended, available for all platforms
- Win32DiskImager — Windows alternative
- dd command — Linux/Mac command line option
Use a quality microSD card (SanDisk, Samsung, or Kingston — 8GB or 16GB, Class 10 or better). Avoid no-name cards — reliability matters for a device running 24/7.
Step 4: Flash the Recovery Image
Insert the prepared recovery SD card into the control board. Power on the miner. The recovery process is automatic — the control board will detect the recovery image and begin reflashing. During this process:
- LED indicators will show the progress (varies by model — consult your model’s manual)
- Do NOT power off or remove the SD card during the process
- The process typically takes 3-10 minutes
- The miner will reboot automatically when complete
Step 5: Verify Recovery
After the miner reboots from the recovery flash, wait 3-5 minutes for full initialization. Try accessing the web interface at the miner’s IP address. If successful, you will need to reconfigure your pool settings, as the recovery flash typically resets all configuration to factory defaults.
Step 6: Remove the Recovery SD Card
Important: After a successful recovery flash on models that boot from internal NAND, remove the recovery SD card. Leaving it in can cause the miner to re-flash on every boot or boot from the SD card instead of the faster internal storage. On models that boot from SD card (S9, etc.), leave the card in place.
Step 7: Replace the SD Card (For SD-Boot Models)
If your miner boots from the SD card (S9, L3+, etc.), replace the old card with the fresh one you prepared. SD cards wear out, and a new card provides reliable boot storage for another 2-3 years.
Advanced Diagnosis
Serial console access: If the miner does not boot at all (no network, no web interface), you can access the bootloader via a serial UART connection on the control board. This requires a USB-to-UART adapter (3.3V TTL level) connected to the debug header pins on the control board. The serial console shows the boot process in real-time, revealing exactly where the boot fails — whether at the bootloader stage, kernel loading, or filesystem mount.
# Typical serial console parameters:
# Baud rate: 115200
# Data bits: 8
# Stop bits: 1
# Parity: None
# Use PuTTY (Windows) or screen/minicom (Linux/Mac)NAND dump and analysis: For NAND-based models where SD card recovery fails, the NAND chip may need to be read with a NAND programmer. This is professional-level diagnostics that can determine whether the NAND chip is recoverable or needs replacement.
When to Get Professional Help
Seek professional ASIC repair if:
- SD card recovery flash does not resolve the boot issue — the control board may have deeper problems
- The SD card slot is physically damaged and the miner cannot read any SD card
- The control board NAND flash has failed and cannot be reflashed via SD card recovery
- You cannot determine the correct hardware version or firmware image for your model
- The control board shows no signs of life (no LED activity) on power-up
D-Central Technologies performs control board diagnostics and repair including NAND flash replacement, SD card slot repair, and firmware recovery for all Antminer models. Submit a repair request here
Affected Models
SD card boot models: S9, S9i, S9j, T9, T9+, L3+, D3, A3, Z9. These models are directly dependent on SD card health. NAND-based models with SD recovery support: S17, T17, S19 series, S21 series. These boot from internal NAND but support SD card recovery when the NAND image is corrupted.
Related Error Codes
- Firmware Update Failed / Bricked Miner — Often the cause of SD card / boot corruption
- Network Error — A partially booted miner may appear as a network error when the web server fails to start
- EEPROM Error — Boot issues can coexist with EEPROM corruption
- Chain X Only — Corrupted firmware can cause chain initialization failures
Frequently Asked Questions
How do I find the correct firmware for my miner?
You need two pieces of information: the exact model number and the hardware (control board) version. The model is on the miner sticker (e.g., “Antminer S19 Pro“). The hardware version is printed on the control board PCB (e.g., “Xilinx V1.2” or “C55 V2.3”). Go to Bitmain’s support page, find your model, and download the firmware matching your hardware version. Using firmware for the wrong hardware version can permanently damage the control board.
Can a bad SD card corrupt my hashboards?
No. The SD card only stores the operating system and firmware for the control board. Hashboard ASIC chips and their EEPROM data are separate. A bad SD card cannot damage hashboards. However, if a corrupted firmware image sends incorrect voltage or frequency commands to the hashboards during a partial boot, it is theoretically possible to cause chip stress — but this is extremely rare.
How often should I replace the SD card?
For miners that boot from SD card (S9, L3+, etc.), replace the microSD card every 2-3 years as preventive maintenance. Keep a backup SD card with current firmware ready so you can swap immediately if the primary card fails. High-endurance SD cards designed for continuous write operations (like those marketed for dashcam use) last significantly longer than standard cards.
My miner’s red light is on but nothing else happens — is it bricked?
A red status LED with no other activity usually means the miner cannot boot from its storage. This is almost always recoverable with an SD card recovery flash. A truly bricked miner (damaged bootloader, fried processor) is rare. Try the SD card recovery process first. If that fails, serial console diagnostics can determine if the control board hardware is functional. Contact D-Central if SD recovery does not work.