ASIC faults: diagnosing and repairing common problems

ASIC faults: diagnosing and repairing common problems

ASIC failures can turn a profitable mining operation into a financial nightmare. With Bitcoin trading at around €59,000, every hour of downtime represents a significant loss of revenue. This guide will help you quickly diagnose the most common problems and apply the correct repair procedures to keep your miners up and running.

Initial diagnosis: identifying the type of fault

Checking for visible symptoms

The first step in the diagnosis is to check the LED indicators on your ASIC. An Antminer S19 or S21 operating normally will display a steady green LED, whilst a red or flashing LED indicates a specific problem:

  • Steady red LED : overheating or power supply issue
  • Flashing red LED : communication error or faulty control board
  • No LED : complete loss of power

Next, check the fans. A silent ASIC is usually a faulty one, as these machines are designed to operate with constant cooling at around 3,000–5,000 RPM.

Analysing system logs

Access your ASIC’s web interface via its IP address to view the operating logs. The most common errors include:


ERROR: Chain[0] disabled
WARNING: Temperature too high (85°C)
ERROR: PSU voltage out of range

These messages will point you towards the source of the problem and save you valuable time during the repair process.

Power supply faults: diagnosis and solutions

PSU (Power Supply Unit) issues

According to field statistics, the power supply accounts for 30 per cent of ASIC failures. A faulty PSU manifests itself as:

  • Sudden shutdown of the miner
  • Unexpected reboots
  • Insufficient voltage (less than 12V at the output)

Solution: Test the output voltage with a multimeter. A healthy power supply delivers 12V ±5%. If the voltage is below 11.4V, replace the PSU with an 80+ Gold-certified model to optimise energy efficiency.

Electrical wiring issues

Check the condition of the PCIe connectors supplying power to the mining cards. Loose or corroded connectors can cause micro-power cuts and damage the ASIC chips.

Checking procedure:

  • Switch off the ASIC completely
  • Unplug and reconnect all connectors
  • Visually inspect the contacts for signs of burning or corrosion
  • Measure the resistance of the cables (should be < 0.1Ω)

Overheating and cooling issues

Diagnosing thermal issues

Overheating is the main cause of reduced hashrate and premature failures. An ASIC overheats when:

  • The temperature exceeds 85°C for a prolonged period
  • The hashrate drops by more than 10% compared to specifications
  • The fans are running at maximum speed (>5000 RPM) continuously

Cooling solutions

Preventative cleaning: Remove the ventilation grilles and clean the heat sinks with compressed air every 3 months. Accumulated dust can reduce cooling efficiency by 25 per cent.

Fan replacement: A faulty fan (speed < 2,000 RPM) must be replaced immediately. Use compatible models (usually 120mm, 12V, 4-pin PWM) to maintain cooling performance.

Temperature Recommended action Impact on performance
< 70°C Normal operation 100% hashrate
70–80°C Enhanced monitoring 95–100% hashrate
80–85°C Enhanced cooling 85–95% hashrate
> 85°C Immediate shutdown Thermal protection

To further optimise your mining revenue by avoiding these thermal issues, see our guide to optimising Bitcoin mining revenue, which details best practices for preventative maintenance.

Hash card failures

Identifying faulty boards

Hash boards contain the ASIC chips that perform the calculations. A faulty board can be identified by:

  • A hashrate reduction of approximately 33% (on a 3-board S19)
  • Abnormally low temperature on a board
  • Repeated errors in the logs: “Chain[X] disabled”

Repair procedure

Swap test: Swap the positions of the boards to confirm that the problem lies with the faulty board and not the connector.

Component-level repair:

  • Visually inspect the capacitors and resistors
  • Test circuit continuity with a multimeter
  • Replace faulty components (requires SMD soldering skills)
  • Re-flash the board’s firmware if necessary

For complex repairs, it is often more cost-effective to replace the entire hashing board rather than attempt a component-level repair.

Network connectivity issues

Diagnosing network faults

An unstable network connection directly impacts mining profitability by increasing the rate of rejected shares. Symptoms include:

  • Intermittent loss of connection to the pool
  • Stale share rate > 2%
  • Inability to access the ASIC’s web interface

Connectivity solutions

Network configuration: Check the IP, DNS and gateway settings. Use a static IP address to avoid DHCP conflicts that may interrupt mining.

Signal quality: A faulty Ethernet cable can cause packet loss. Test with a new Cat6 cable and check the RJ45 connectors for damage.

To further optimise your network connection and reduce interruptions, our guide to reducing the stale rate in Bitcoin mining will provide you with advanced technical solutions.

Preventative maintenance and essential tools

Basic tool kit

To carry out effective diagnostics and repairs, put together a kit containing:

  • A multimeter for measuring voltages and resistances
  • Precision screwdrivers to access components
  • Compressed air for cleaning heat sinks
  • High-quality thermal paste for refitting heat sinks
  • Spare Ethernet and PCIe cables

Preventative maintenance programme

Establish a rigorous maintenance schedule:

Weekly: Check temperatures and hash rate

Monthly: Clean the air filters and carry out a visual inspection

Quarterly: Thorough cleaning of radiators and checking of connections

Half-yearly: Replace thermal paste and calibrate fans

This proactive approach can reduce breakdowns by 70 per cent and extend the lifespan of your ASICs by 2–3 years.

When to call in a professional

Some repairs require advanced technical expertise:

  • Replacement of individual ASIC chips
  • Repair of multilayer printed circuit boards
  • Issues with corrupted firmware
  • Damage caused by lightning or power surges

In such cases, please contact a specialist repair centre or consider purchasing a replacement miner from our catalogue to minimise disruption to your mining operations.

Conclusion: maintaining the profitability of your mining farm

Mastering the diagnosis and repair of ASIC faults is essential for maintaining the profitability of your mining operation. With Bitcoin at €59,000 and an average yield of 0.00000054 BTC per TH/day, every hour of downtime represents a significant loss of revenue for a farm with a capacity of several tens of TH/s.

Power supply, overheating and connectivity issues account for 80 per cent of common faults, but can be resolved with the right procedures and tools. Investing in a preventative maintenance programme and building up a stock of spare parts will save you thousands of euros in avoided downtime.

To further optimise your mining infrastructure and monitor your equipment effectively, create an account on our platform and benefit from advanced monitoring tools that will alert you at the first sign of a fault.

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