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How to Modify an APW12 PSU for 120V AC Use: A Comprehensive Guide

Table of Contents

The Bitmain APW12 Power Supply Unit (PSU) is an integral component in the cryptocurrency mining infrastructure, designed to deliver robust and reliable power to high-performance mining rigs such as the Bitmain Antminer X19 and X21 series. Under its standard configuration, the APW12 requires an input voltage of 200V to 240V AC, aligning with industrial power standards available in commercial or advanced home mining setups.

However, the typical residential power infrastructure in North America provides 120V AC, which poses a significant barrier for individual miners or small-scale operations not equipped with industrial-grade electrical installations. This discrepancy in power requirements can limit the feasibility and economic efficiency of deploying high-end mining equipment in residential areas.

Techniques for modifying the APW12, such as those shared by PivotalPleb, not only enhance individual mining setups but also contribute to the broader mining community by sharing knowledge and practical solutions to common challenges.

This guide provides a comprehensive overview of the steps required to modify an APW12 PSU for 120V use, following the pioneering techniques shared by the mining community, and ensuring that the process is approached with safety and efficiency as primary concerns. By adapting the APW12 PSU to be more versatile in its operational voltage, miners can optimize their setups based on the available infrastructure while minimizing additional investment.

Necessary Tools and Materials

To successfully modify the APW12 PSU for 120V use, having the right tools and materials is essential. This ensures that the modification process is not only effective but also safe. Below is a comprehensive list of all required items:

Tools Required

  1. Phillips Screwdriver: Used for opening the PSU casing and accessing internal components.
  2. Soldering Iron (70W or higher): Necessary for soldering new components onto the PCB. A high-wattage iron ensures efficient heat transfer, which is crucial for solid solder joints.
  3. Sharp Scraping Tool: This tool is used to remove the conformal coating from the PCB around the soldering areas without damaging the board.
  4. Wire Cutters: For trimming the resistor leads to the appropriate length before soldering.
  5. Multimeter: To test the PSU outputs and ensure that modifications have not affected other functional aspects of the PSU.
  6. Insulating Gloves: To protect against electric shock while handling the PSU during and after modification.
  7. Safety Goggles: To safeguard eyes from potential sparks or debris during the modification process.
  8. Non-conductive Work Surface: Ensures that the PSU and its components do not come into accidental contact with conductive surfaces, which could cause shorts.

Materials Needed

  1. 1 MΩ, 0.25 W Axial Resistors: Two of these resistors are needed to modify the brown out detector circuits for 120V compatibility.
  2. Conformal Coating Remover (optional): If available, this can simplify the process of removing the protective coating from the PCB, making it easier to solder new components.
  3. Lead-free Solder: To attach the new resistors securely to the PCB.
  4. Solder Wick/Braid: Helps remove any excess solder or correct mistakes during the soldering process.
  5. Heat Shrink Tubing or Electrical Tape: To insulate exposed leads or wires after modification, ensuring safety and reliability.
  6. Isopropyl Alcohol and Lint-free Cloth: For cleaning the PCB areas before and after soldering to ensure a clean work environment and prevent contamination of the components.

Each tool and material listed plays a crucial role in the modification process. Proper use of these items will help achieve a successful conversion of the APW12 PSU to work efficiently on a 120V AC supply, ensuring both performance stability and operational safety.

Safety Precautions

When modifying the APW12 PSU to operate on 120V AC, it is crucial to follow stringent safety measures to prevent electrical shocks and avoid damaging the equipment. The following guidelines provide comprehensive safety protocols to ensure a safe and successful modification process.

Preventing Electrical Shock

  1. Disconnect the Power Supply:
    • Complete Power Shutdown: Ensure the PSU is completely powered off and disconnected from any power sources. This includes disconnecting it from the mains supply and any connected devices or hardware.
    • Verification: Double-check that all connections, including power cords and associated cables, are fully disconnected to ensure there is no power flow to the PSU.
  2. Discharge Capacitors:
    • Residual Charge: Capacitors within the PSU can retain charge even after the power is disconnected, capable of delivering a dangerous shock.
    • Safe Discharge Procedure:
      • Attach a resistor (typically around 10kΩ to 100kΩ, 5-watt resistor) to insulated, alligator clip leads.
      • Carefully connect the leads across the capacitor terminals for several seconds to allow the capacitor to discharge safely through the resistor.

Handling High-Voltage Components

  1. Use of Personal Protective Equipment (PPE):
    • Insulating Gloves: Wear rubber or other insulating gloves to protect against electrical shocks.
    • Safety Goggles: Always wear safety goggles to protect your eyes from potential sparks or debris during the modification process.
  2. One-Hand Rule:
    • To reduce the risk of electric shock passing through the heart, use only one hand at a time to perform electrical work. Keep the other hand away from all conductive materials.
  3. Proper Use of Tools:
    • Insulated Tools: Ensure that all hand tools used are insulated to prevent accidental electrical conduction.
    • Cautious Handling: Be careful with metal tools near the PSU’s PCB to avoid creating shorts between components.

General Equipment Handling

  1. Secure Work Environment:
    • Non-Conductive Surface: Perform all modifications on a non-conductive surface to prevent accidental electrical conduction.
    • Organized Workspace: Maintain an organized workspace to avoid unintentional contact with electrical parts and ensure quick access to necessary tools.
  2. Component Handling and Storage:
    • Static Sensitivity: Use a grounded wrist strap and work on an anti-static mat to prevent static discharge that can damage electronic components.
    • Gentle Handling: Only handle electronic components by their edges and avoid touching component pins or circuits directly.

Soldering Safety

  1. Well-Ventilated Area:
    • Fume Extraction: Soldering can produce harmful fumes; work in a well-ventilated area or use a fume extraction system to minimize inhalation of these fumes.
  2. Heat Safety Precautions:
    • Soldering Iron Placement: Always place the soldering iron in its stand when not in use and be aware of the hot end which can cause burns.
    • Molten Solder: Be cautious of splashes from molten solder which can also cause burns.

Post-Modification Testing

  1. Visual Inspection:
    • Before powering the PSU, conduct a thorough visual inspection to check for any loose connections, misaligned components, or solder splashes that could short-circuit the board.
  2. Initial Power On:
    • Use a surge protector with an overload circuit during the initial power test to protect against potential shorts and provide an additional safety layer.

By adhering to these safety measures, you can ensure that modifying your APW12 PSU is both a safe and effective process, thereby preventing any potential injuries or damage to the equipment. Always prioritize safety and double-check each step to maintain the integrity and functionality of your PSU.

Step-by-Step Modification Guide

This guide outlines the detailed steps required to modify an APW12 PSU to operate on 120V AC, enabling its use in standard North American residential settings. By following this guide, you can safely adjust the PSU’s input voltage compatibility.


  1. Disconnecting the PSU:
    • Ensure the PSU is completely powered off.
    • Unplug all connections, including power cables and any connections to mining rigs or other hardware.
    • Allow the PSU to sit unplugged for at least 10 minutes to ensure all internal capacitors are fully discharged.
  2. Preparing the Work Area:
    • Clear a well-lit, organized workspace on a non-conductive surface.
    • Gather all necessary tools and materials outlined in the “Necessary Tools and Materials” section.
    • Put on safety goggles and insulating gloves to protect against potential electrical shocks and debris.
  3. Opening the PSU Casing:
    • Use a Phillips screwdriver to remove screws securing the top cover of the PSU.
    • Carefully lift the top cover off and set it aside.
    • Take a moment to visually inspect the interior for any obvious signs of damage or wear that could affect the modification process.

Accessing the Internal Components

  1. Removing the Top Cover:
    • With the screws removed, gently lift the top cover to expose the internal components. Ensure all screws are stored safely during this process.
    • Observe the arrangement and secure any loose cables that could obstruct work on the PCB.
  2. Accessing the PCB:
    • Identify and unscrew the PCB mounting screws that secure the circuit board in place. Take care to keep track of all screws and their respective locations.
    • Carefully lift the edges of the PCB to partially remove or tilt it for better access to the underside of the board.
  3. Identifying Critical Components:
    • Locate the brown out detectors on the PCB; these are typically marked and near the power input connectors.
    • Take note of any sensitive components, particularly capacitors and connectors, that should be avoided during soldering.

Modifying the Brown Out Detector Circuits

  1. Locating the Resistor Networks:
    • Find the resistor networks associated with each brown out detector. These are usually located near the input stages of the PSU.
    • Confirm the resistor values and configurations as per the PSU schematic or modification guide.
  2. Preparing for Soldering:
    • Use a sharp scraping tool to carefully remove the conformal coating from around the resistor pads where new resistors will be added.
    • Clean the area with isopropyl alcohol and a lint-free cloth to ensure a clean soldering surface.
  3. Soldering the Resistors:
    • Position the 1 MΩ, 0.25 W axial resistors across the designated pads.
    • Solder each resistor into place, making sure to maintain a steady hand to avoid bridging connections with excess solder.
    • Double-check your work to ensure that no adjacent components are touched or damaged.

Reassembly and Initial Testing

  1. Reassembling the PSU:
    • Carefully place the PCB back into its original position within the PSU enclosure.
    • Secure the PCB with its mounting screws and ensure that no wiring is pinched or improperly placed.
    • Reattach the top cover of the PSU and secure it with the previously removed screws.
  2. Initial Testing:
    • Connect the PSU to a 120V AC source via a surge protector.
    • Power on the PSU and observe any immediate signs of failure, such as sparks or unusual noises, which could indicate a problem.
    • Use a multimeter to check the output voltages at the specified test points to confirm that the PSU operates correctly under the new voltage conditions.

By following these detailed steps, you can successfully modify an APW12 PSU to operate on 120V AC, making it suitable for home mining applications. Ensure all safety precautions are followed closely to avoid any incidents during the modification process.

Final Testing and Setup

After successfully reassembling the modified APW12 PSU, the next crucial steps involve safely connecting it to a mining rig and conducting final testing to ensure optimal performance. This phase is vital for confirming the reliability and safety of the PSU under operational conditions.

Connecting the PSU to a Mining Rig

  1. Safety Inspection:
    • Before connecting the PSU to any devices, conduct a final inspection to ensure all screws are tightened, no loose components are present, and the workspace is clear of unnecessary materials and tools.
  2. Connecting the PSU:
    • Power Connection: Connect the PSU to a 120V AC outlet using a surge protector. This adds an additional layer of safety, protecting against potential electrical surges.
    • Rig Connection: Attach the power cables from the PSU to your mining rig. Ensure that connections are secure and that the polarity of the connections matches the requirements of the mining hardware.
  3. Initial Power On:
    • Turn on the PSU without powering the entire mining rig. Observe the PSU fan and listen for any abnormal sounds. Initial power on should be smooth with the fan operating at a consistent speed.
    • Check the voltage outputs using a multimeter at the output terminals to ensure they match the specifications necessary for your mining rig.

Final Testing

  1. Power the Mining Rig:
    • Once the PSU is confirmed to be working correctly at no load, power on the mining rig.
    • Monitor the startup sequence of the rig to ensure that all components are functioning correctly and the system boots without errors.
  2. Monitor PSU Performance:
    • Voltage and Current: Continuously monitor the voltage and current outputs using a multimeter or an integrated digital monitoring tool if your PSU has one. Ensure that the voltage does not fluctuate beyond the component specifications.
    • Temperature: Check the temperature of the PSU and the mining rig to ensure there is no overheating. Use thermal sensors or your hand to detect unusually hot areas.
  3. Adjust Settings for Optimal Operation:
    • Load Balancing: If the PSU supports multiple outputs, balance the load across these to maximize efficiency and minimize wear on the PSU components.
    • Underclocking: Consider underclocking the mining rig to reduce the power consumption and stress on the PSU. This is particularly beneficial in setups where the PSU is operating near its maximum capacity.
  4. Continuous Monitoring:
    • Set up a system for continuous monitoring of the PSU’s performance. This can include software tools that log performance metrics or physical monitoring equipment like a power meter.
    • Regularly check connections and cables for signs of wear or damage, and replace them as necessary to maintain safety and efficiency.

Tips for Monitoring and Adjustment

  • Use Reliable Instruments: Always use accurate and calibrated instruments for testing electrical parameters to ensure you are getting reliable data.
  • Software Tools: Utilize PSU and mining rig software tools available to monitor power draw, efficiency, and overall performance. These tools can provide alerts and automate adjustments based on predefined criteria.
  • Environmental Considerations: Keep the mining setup in a well-ventilated area to avoid overheating. Environmental controls like AC or fans can be necessary depending on the rig’s location and ambient temperatures.

By following these detailed steps for final testing and setup, you ensure that your modified APW12 PSU operates safely and efficiently, providing stable power to your mining rig. Regular maintenance and monitoring are crucial to sustain optimal performance and prolong the lifespan of your mining hardware.

Troubleshooting Common Issues

Even with careful modification, the APW12 PSU may encounter issues that affect its performance or stability. Understanding how to troubleshoot these common problems is essential for maintaining an efficient mining operation. Here are some typical issues you might face and the appropriate solutions:

Common Problems and Solutions

  1. PSU Doesn’t Power On:
    • Check Connections: Ensure all cables are securely connected, and the PSU is properly plugged into the 120V AC outlet. Verify that no fuses have blown in the PSU or your power strip/surge protector.
    • Inspect for Short Circuits: Re-open the PSU casing and check for any signs of shorts, such as solder bridges, especially around the newly installed resistors.
    • Capacitor Discharge: Ensure capacitors were fully discharged before beginning work on the PSU. Residual charge can cause damage during modification.
  2. PSU Powers On But No Output:
    • Voltage Testing: Use a multimeter to test the output voltages at the PSU outputs. Compare these readings against the expected values.
    • Resistor Placement: Double-check the placement and soldering of the 1 MΩ resistors to ensure they are correctly installed according to the modification instructions.
  3. Overheating:
    • Adequate Ventilation: Confirm that the PSU’s fan is operational and the ventilation is not obstructed by dust or debris. Ensure the PSU is in a well-ventilated area.
    • Load Adjustment: Reduce the load on the PSU if it is nearing its maximum capacity. Overloading the PSU can cause excessive heat build-up.
  4. Voltage Fluctuation:
    • Secure Connections: Loose connections can cause unstable voltage outputs. Check all connections for tightness.
    • Component Check: Verify that all components, especially capacitors and resistors, are functioning correctly. Replace any faulty components.
  5. Noise from the PSU:
    • Fan Issues: If the noise is coming from the fan, ensure that the fan is clear of obstructions and is not failing.
    • Electrical Noise: Buzzing or humming can indicate a load issue or an electrical fault within the PSU. Review electrical loads and reduce if necessary.

Reverting Modifications

If you encounter persistent issues with the modified PSU or prefer to return it to its original specifications, follow these steps to revert the changes:

  1. Safety Preparations:
    • Disconnect the PSU and ensure it is completely powered off. Follow the same safety measures as during the modification, including discharging capacitors.
  2. Remove Added Components:
    • Open the PSU casing and carefully de-solder the 1 MΩ resistors that were added during the modification. Ensure that no traces or pads are damaged in the process.
  3. Restore Original Settings:
    • If any original components were removed or altered (other than the addition of resistors), replace them with the same type and specification as originally used.
  4. Inspect and Clean:
    • Check the entire board for any residual solder or debris that could cause a short. Clean the board with isopropyl alcohol and a lint-free cloth.
  5. Reassembly and Testing:
    • Carefully reassemble the PSU, ensuring all screws and connections are secure. Test the PSU in its original configuration to ensure it functions correctly.

By effectively troubleshooting and knowing how to revert modifications if necessary, you can maintain the operational integrity and safety of your APW12 PSU. Regular monitoring and maintenance will help detect issues early and extend the lifespan of your mining equipment.


Modifying the APW12 PSU to operate on 120V AC provides substantial benefits for those involved in home mining and small-scale operations. This adaptation allows for the use of high-performance mining equipment within the typical residential electrical infrastructures of North America, thereby eliminating the need for costly industrial-grade installations. By enabling the APW12 PSU to function efficiently on a standard residential voltage, miners can greatly increase the accessibility and flexibility of their operations. This not only makes setting up a mining operation more economical but also broadens the possibilities for mining location choices, without the limitations imposed by higher voltage requirements.

The modification of the APW12 to 120V use must be approached with meticulous attention to safety. Ensuring that all safety protocols are strictly followed during the modification process is critical. This includes the use of personal protective equipment, proper discharge of capacitors, and rigorous testing of all connections once the PSU is reassembled. Regular maintenance and monitoring post-modification are essential to ensure the PSU operates safely and efficiently. Miners should continually inspect their equipment for signs of wear and potential failure, and maintain an environment that prevents overheating and maximizes the longevity of their PSU.

For those who may feel uncertain about undertaking such modifications independently, or who prefer the assurance that comes with professional services, D-Central offers a viable solution. D-Central Technologies specializes in providing modified APW12 PSUs that are ready to use on 120V circuits. Additionally, they offer services to modify your existing PSUs, ensuring that all modifications meet the highest standards of safety and performance. This service is invaluable for miners who wish to optimize their setups for residential use while mitigating the risks involved in modifying high-voltage electrical equipment.

In conclusion, while the benefits of modifying the APW12 PSU for 120V use are clear, it is imperative to prioritize safety and precision throughout the process. If you are considering such a modification but are hesitant about the technical challenges, consult with the professionals at D-Central Technologies. They can provide both the modified PSUs and the expertise needed to safely adapt your existing equipment. This approach not only ensures a higher degree of safety but also enhances the efficiency and effectiveness of your mining operations.


What is the Bitmain APW12 Power Supply Unit (PSU) used for?

The Bitmain APW12 Power Supply Unit (PSU) is designed to power high-performance cryptocurrency mining rigs, specifically the Bitmain Antminer X19 and X21 series, providing robust and reliable power for efficient mining operations.

Why modify the APW12 PSU for 120V use?

Modifying the APW12 PSU for 120V use allows it to operate on standard North American residential electrical infrastructures, which typically provide 120V AC. This modification expands the accessibility and flexibility of mining operations by enabling the use of high-performance equipment without needing industrial-grade electrical installations.

What are the necessary tools and materials for modifying the APW12 PSU?

Key tools include a Phillips screwdriver, a high-wattage soldering iron, a sharp scraping tool, wire cutters, a multimeter, insulating gloves, and safety goggles. Materials needed comprise 1 MΩ, 0.25 W axial resistors, conformal coating remover (optional), lead-free solder, solder wick/braid, heat shrink tubing or electrical tape, and isopropyl alcohol with a lint-free cloth.

What safety precautions should be followed when modifying the APW12 PSU?

Important safety precautions include disconnecting the power supply and ensuring it’s off, discharging capacitors, using personal protective equipment (PPE) like insulating gloves and safety goggles, following the one-hand rule to minimize the risk of electric shock, and ensuring all modifications are done on a non-conductive work surface.

Can the APW12 PSU modified for 120V operation revert to its original setup?

Yes, the modifications to operate on 120V can be reverted. This process involves safely discharging capacitors, de-soldering the added 1 MΩ resistors, and restoring any altered original components back to their initial state, followed by a thorough inspection, cleaning, reassembly, and testing of the PSU.

Where can I get professional help for modifying my APW12 PSU?

D-Central Technologies offers services to modify APW12 PSUs to operate on 120V circuits, providing an efficient and safe solution for miners. They also offer ready-to-use modified PSUs for those looking to optimize their mining setups for residential use with enhanced safety and performance standards.

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