Why Power MOSFETs Fail in Miners and the Risks of Poor Repairs
Introduction
Power transistors (MOSFETs) on modern miner boards are not just passive components in the power circuit. They are critical elements of the power management system that enable power delivery to ASIC chips only after passing all required safety checks.
These high-current switches are controlled by the main control board. The system is engineered so that power is supplied only after diagnostics, thermal checks, and interface validation. This is a deliberate design for protecting the miner’s core hardware.
Role of Power Switches on Miner Boards
Each hashboard in a miner delivers tens or even hundreds of amps to a dense grid of ASIC chips. But chips should not receive power the moment the unit is powered on. Instead, controlled sequencing is implemented.
Power MOSFETs act as electronic switches, triggered only after all conditions are met. Their key roles:
- Keep ASICs disconnected from power until explicitly enabled
- Allow immediate shutdown in case of faults
- Protect the board by breaking the circuit during overcurrent or overtemperature
Why Power MOSFETs Fail
🔥 1. Short Circuits in the Load (ASIC Chips)
One of the most common reasons for MOSFET failure is a short circuit in the chip power line. This could be due to:
- Internal failure in one of the ASIC chips
- Contamination: dust, dirt, or moisture creating conductive paths
- Thermal degradation of chip structures
When the transistor receives the “ON” command, it begins to conduct. Normally, current flows through ASIC chips connected in series. But with a short, current is redirected into a low-resistance path, rapidly exceeding safe limits. The MOSFET overheats and physically breaks down within milliseconds.
🌡️ 2. Partial Gate Drive (Undervoltage on the Gate)
To fully open a power MOSFET, the gate must receive a specific voltage. If gate control circuits are damaged or degraded, the gate may receive only partial voltage, leaving the transistor in linear mode instead of fully on.
In this mode, the transistor behaves like a resistor:
P = I² × R = 40² × 1 = 1600 W
This energy is concentrated in the chip core. Even short bursts cause thermal destruction, melted silicon, and lifted pads.
🔧 3. Inadequate Heat Dissipation
Miner hashboards do not use screw-on heatsinks above the transistors. Heat is conducted through internal copper layers and a soldered metal base underneath the MOSFET.
If that soldered interface is weak — due to oxidation, poor solder flow, or uneven preheating — thermal resistance increases. At 40–60 A and only 2 mΩ resistance, the power loss reaches 4–8 W. Without efficient dissipation, localized hot spots burn out the device.
⚡ 4. Gate Driver Circuit Failure
Even with a good MOSFET, failure in the gate control path can prevent it from operating correctly:
- No gate voltage = circuit never closes
- Fluctuating gate signal = transistor flickers open/closed, overheating itself
What Happens in a Bad Repair
A proper repair includes:
- Replacing the faulty transistor with a working one
- Restoring the gate driver circuit
Unfortunately, some repair attempts bypass this entirely. Instead of fixing the gate logic, the technician bridges the MOSFET with solder or wire, creating a permanent connection between input and output.
This disables control from the mainboard. Now, the ASIC chips receive power immediately upon boot — with no diagnostics, no delay, and no protection.
Consequences of Shunt Repairs
🔥 Power Delivered to ASICs Too Early
Without sequencing, ASICs are energized before thermal and logical checks. If even one chip has a defect, the full power rail slams into it — potentially destroying the chip, board, or power supply.
💣 No Protection Against Short Circuits
A properly working gate logic can shut off the transistor during faults. But when the transistor is bypassed with a wire, there is no way to stop the current.
The result: burned-out ASICs, vaporized power traces, blown capacitors — and in extreme cases, the board burns to charcoal.
⚠️ Loss of Power Control
The control board cannot shut down the hashboard even in critical cases:
- Thermal sensor disconnected or failing
- Excessive temperature during overclocking
- Manual power cycle required, but not possible remotely
Why Proper Repair Matters
✅ Restores Safe Startup Logic
Only a working power gate system ensures ASICs are powered after validation, and can be turned off on demand.
✅ Enables Safe Diagnosis and Monitoring
With working logic, you can analyze startup stages, detect thermal behavior, and collect logs during issues.
✅ Prevents System-wide Damage
One faulty or bridged hashboard can crash the entire miner — tripping power supplies, overloading buses, or damaging adjacent boards.
✅ Reduces Long-Term Risk and Cost
A shunted board is a time bomb. It may work today — but the next boot cycle could destroy it entirely.
If that happens, the cost of repair won't match the standard rate, but will be at least double (see our repair pricing), and may result in needing a full board replacement or even a new miner.
Conclusion
Power MOSFET failure is serious, but fixable. Attempting to “solve” it by shorting around it is not repair — it’s sabotage.
A proper repair:
- Restores transistor switching control
- Re-enables protection logic
- Prevents overheating and component failure
- Extends miner lifespan
💡 If your miner’s power transistor has failed — do not allow shunt-based repairs. Full functional restoration is the only way to ensure long-term reliability and safety.
If you're facing this issue, don't take risks — contact our team right away for a professional evaluation and repair.