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Crypto Miners Direct

Maintenance guide

Control Board Replacement

Confirm that a miner's control board is the fault, identify a compatible replacement, fit it safely and bring the machine back with correct firmware.

Published October 1, 2026 · Reviewed by James Emerson

Replace a control board only after ruling out the network, the power supply and a corrupted firmware image, because all three imitate a dead board. The replacement must be the board type for your miner family and hardware platform, loaded with firmware for your exact model. The swap itself is a matter of covers, cables and a few screws, but the details differ by model, so follow the manufacturer's procedure. Opening the machine or fitting a non-original control board can affect warranty.

Key points

  • Try recovery first: check the network cable and switch, reset to factory settings, then re-flash firmware by SD card using the manufacturer's procedure.
  • No lights can mean no power reaching the board, not a failed board. Check the power supply first.
  • Match the board to the miner family and platform, and load firmware for the exact model. A wrong combination can leave the board unusable.
  • Power off and unplug before opening the machine, and take static precautions.
  • Do not interrupt power while new firmware is installing or initialising.

What the control board does

The control board is the miner's computer. It runs the firmware and web interface, connects to the network and the mining pool, hands out work to the hashboards over signal cables and collects their results, reads temperature sensors, drives and monitors the fans, and tells the power supply what voltage to deliver. It also stores your pool and network settings.

Symptoms that point to the control board

Symptom Control board Power supply Hashboard Network
Power supply fan runs, miner does not start Likely if the board's supply is present Likely if it is not No No
Ethernet port lights off, miner otherwise running Possible No No Cable or switch first
No IP address, cannot be found on the network Likely after cable and switch are ruled out No No Check first
Firmware will not upgrade, SD card flash fails Likely No No No
A fan port reads wrong with a known-good fan Likely No No No
One board missing whichever cable is used on one port Likely, that port No Possible No
One board missing on any port No Possible Likely No

Bitmain's documentation gives these pointers. Its indicator-light guide gives both status lights off as a control board fault, to be recovered by SD card or replaced. Its fan guidance says a fault that remains with a good fan fitted means the control board is damaged. Its start-up guidance says that when the power supply fan runs but the miner does not start, the control board's 12 V supply should be checked: no 12 V points to the power supply, and 12 V present with the fault remaining points to the control board. That measurement is made on live equipment and is for someone trained to do it safely.

Rule these out before buying a board

  1. Network. Reseat or replace the Ethernet cable and try another switch port. Do not connect miners to PoE (power over Ethernet) switch ports; Bitmain warns this burns the control board.
  2. Power to the board. With the machine unplugged, reseat the control board's power and power supply control cables. Try a known-good power supply of the correct model.
  3. Factory reset. On Antminers, Bitmain's reset-button method works only between 2 and 10 minutes after power-on: hold Reset for 5 seconds, and the miner restores settings and restarts within about 4 minutes.
  4. Firmware recovery. Re-flash using the manufacturer's SD card procedure for your model. Bitmain's sequence for a miner with no data is restart, reset, flash firmware, restart; only if that fails is the control board treated as faulty.

Identifying the correct board

A control board that fits the case is not necessarily the right one. Check:

  • Family and platform. Boards are made for a family of models, and the same model can ship with control boards built around different processors. Firmware is built per platform, so note the part number and markings on the old board and order the same type.
  • Connectors. Signal, fan and power connectors must match. MicroBT's air-cooled WhatsMiner control board, for example, takes a 14-pin power supply flat cable, a 22-pin adapter board flat cable and a 4-pin fan cable.
  • Firmware on arrival. A new board may not arrive with your model's firmware. Bitmain's instructions for new S19 control boards say they may come pre-set with S17 or S19j Pro firmware and must be upgraded to the correct, latest firmware for the model.
  • One-way steps. Bitmain warns that on S19 control boards, after upgrading and restarting you must wait more than 30 seconds without cutting power while a one-time programmable function is enabled. A power loss in that window can leave the board unable to start, and once enabled, the main control chip cannot be used on other models.

Warranty points: Bitmain states a 180-day warranty for separately purchased control boards. It also defines a machine whose control board or hashboards are not its original parts as a mixed-board machine, which voids the miner's warranty. MicroBT's policy excludes damage from disassembly without its authorisation and from unofficial accessories, naming control boards. For a machine under warranty, a manufacturer repair ticket is the safer route. Parts are listed under control boards.

Before you start

  • Record the pool and network settings if the old board still responds.
  • Download the correct firmware and recovery image for your model from the manufacturer.
  • Shut down, switch off and unplug the power cords. Bitmain states that working on a plugged-in miner damages the control board.
  • Wear an anti-static wrist strap and handle the board by its edges.
  • Photograph every cable before unplugging it.

General replacement procedure

  1. Remove the cover over the control board.
  2. Unplug every cable from the board by its connector housing: hashboard signal cables, fan cables, the power cable and the power supply control cable.
  3. Release the board, which slides out or is held by screws in a carrier.
  4. Compare old and new boards: same connectors in the same places, same markings.
  5. Fit the new board and reconnect every cable to the position it came from. Connectors should seat without force; MicroBT warns that flat cables must not be forced in reversed.
  6. Refit the covers, checking that buttons, lights and the Ethernet port line up with their openings.

Two manufacturer procedures, summarised:

  • Bitmain, integrated-PSU Antminers. Remove the screws of the control board cover, hold down the round button and lift the cover off. Remove the two screws of the front bezel. Unplug the hashboard cables, fan cables, control board power cable and voltage regulator cable. Push the control board forward to the end of its travel to remove it.
  • MicroBT, air-cooled WhatsMiner. Unplug the fan cable from the control board and remove the four screws holding the control board housing to the case. Unplug the power supply flat cable and the adapter board flat cable. Remove the four screws holding the board in its housing. Installation is the reverse.

If the manual for your exact model differs from these steps, follow the manual.

Firmware and SD card recovery

In general terms, recovery means writing a manufacturer recovery image to a memory card, booting the control board from it so that it rewrites its internal storage, then removing the card and restarting. The image, card preparation and wait times are model-specific, so use the manufacturer's tutorial for your model.

Points Bitmain makes about its own process:

  • The SD card must be formatted as FAT32, and the flash package must be decompressed and its contents copied to the root of the card.
  • Failed card flashes are usually caused by a badly prepared card.
  • If a power failure during an upgrade leaves the board unable to upgrade or flash, it generally needs repair.

Bitmain notes that a reset returns the miner to its original firmware. After any recovery, upgrade to the current firmware for the exact model and re-enter pool and network settings.

Post-replacement checks

  1. Power on and watch the indicator and Ethernet lights.
  2. Find the machine on the network. A new control board has a new MAC address, so it will usually receive a new IP address.
  3. Log in, set a new password, and confirm the model and firmware version shown.
  4. Confirm every hashboard is detected with its full chip count and every fan is detected with a plausible speed.
  5. Enter pool settings and confirm shares are accepted at the pool.
  6. After the machine has settled, compare average hashrate and temperatures with its records, and note the new board's serial number.

When to stop and use a repair service

  • The machine is under warranty.
  • The new board does not detect hashboards that worked before.
  • A recovery flash fails twice with a correctly prepared card.
  • You find burn marks, corrosion or liquid on the old board or its connectors. Another fault may have damaged it.
  • You cannot identify the board type with confidence.

Open a repair ticket with the manufacturer or use a qualified repair centre, and send the log, photos and the results of your checks. Hashboard Troubleshooting lists what to gather.

Sources