Repair of the ASIC power supply

An ASIC power supply is a complex electronic device that provides consumers (hash boards and control board) with stable electrical energy with specified parameters. The performance of the connected devices depends on the high-quality voltage supplied by the UPS. You can understand the principle of operation, learn how to properly repair the power supply units of miners and other electronic devices by completing training in UPS repair. 

Types of ASIC power supplies

The current consumption during the operation of an electronic device can fluctuate significantly. This has a negative effect on the operation of its various units. Therefore, the UPS must be selected for the peak power consumption. The maximum power consumed by the miner can be calculated using the formula: 

P = U * I

where:

U – the output voltage is 12 volts

I – max consumer current (connected load), measured in Amperes. When choosing a PSU for ASICs, you need to study the factory documentation for the miner

P – the power of the source is measured in watts.

There are two main types of PSUs:

• with high output voltage and low currents 1-10 Ampere,
• with low output voltages and high output currents (welding inverter, ASIC miners). 

Powerful electronic components depend on the quality of the incoming voltage. And this is usually the high-quality operation of low-current UPS units.

To connect ASICs, a wide variety of power sources are used that provide the necessary power to the load for the stable operation of hashboards. The most common power supplies for miners are: APW3, APW7, APW8, APW9, APW12, Ant, Avalon.

Purpose of power supplies

UPS failure occurs much more often than other electronic components. This primarily depends on the quality of electrical energy, the correct connection of the load to the power source in terms of power, the quality of the connections in the connectors (connectors).

The ASIC power supply is a high-voltage unit for primary circuits, consists of radio components, operates at an alternating current frequency of 50 Hz. 

Almost all power supplies perform similarly. PSMPUs perform the following functions:

• rectification voltage
• stabilization, voltage conversion
• voltage change
• protection against overloads and short-circuit currents. 

UPS advantages and disadvantages

The manufacture of blocks is carried out by various circuit designs. To change the voltage, transformers are used, less often capacitors are used. A PSU is used to stabilize the voltage and protect against ASIC overloads. 

Benefits of using a UPS:

• small size
• high efficiency reaching 90%
• wide range of input voltage from 100 to 250V
• relatively low manufacturing cost
• insensitive to power quality
• remote control capability

Disadvantages of using a UPS:

• high level of interference
• complex circuitry
• high thermal conditions
• Low reliability
• There is no possibility of self-repair without knowledge of electronics

PSU Repair Tools

To repair low-power ASIC power supplies, you can use a soldering station, for example Quick 861DE. For more powerful ones, a soldering iron is needed with a constant soldering temperature of 300-350 degrees Celsius and a power above 80 W for soldering power elements (diode assemblies and transistor switches used in miners’ power supplies). To avoid damage to the printed circuit board, it is necessary to warm it up with a hair dryer with an outlet temperature of 260 degrees Celsius with an average air flow.

To check the condition of electrical circuits, you must use a multimeter. Use tweezers to solder small parts. Dismantle the power keys using a desoldering pump. An oscilloscope is also required to test the operation of PWM controllers.

How to learn how to repair ASIC power supplies

An ASIC repair technician needs:

• have some knowledge of electronics
• understand the principles of operation of all electronic elements
• know the laws of electronics (Ohm’s, Kirchhoff’s law)
• understand the processes taking place in the block
• be able to read electronic circuits
• own the technology of soldering SMD components and BGA chips

The sequence of diagnostics and repair of the UPS:

1. Perform a visual inspection of the device for mechanical damage (cracks, chips, burnt parts, darkening of the printed circuit board due to heavy load or improper operation).
2. Pay attention to the condition of the wires and connectors
3. Discharge the capacitor of the mains filter. For discharge, it is recommended to use a powerful resistor, and in its absence, an ordinary 220 V incandescent lamp with a power of at least 60 W. Then measure the voltage across the capacitor of the mains filter, which should not be more than 5 V.
4. Carry out cleaning from dirt (settled dust, traces of insects).
5. When repairing, you must pay attention to the deformation of the printed circuit board, darkening of power resistors, burst fuses, short circuit on the board.
6. After replacing defective components, there should be no deviations from the standards according to the schematic diagram of the device. Otherwise, the installed elements will fail.

Repair of the power supply unit ASIC APW8

The number of ASICs is increasing on the territory of the Russian Federation. Investors enter crypt mining by increasing the country’s hash index for mining BTC, not always purchasing new equipment that often breaks down. Periodically our SC receives out-of-order powerful power supplies APW7, APW8, APW9, as well as their modifications.

Let’s consider the structure and principle of operation of PSMPU data. Since the principle of their operation is similar, we will take APW8 for the example under consideration.

APW8 power supply unit consists of:

• two fans
• printed circuit board
• two cases (upper and lower)
• network input 220 V
• two output voltages 12 V each

The main voltage output is controlled by the PIC port, and the constant U of different models varies from 8 to 20.04 V. The main unit current output is adjustable to 110 A, the auxiliary board fixed current output to 5 A.

This PSMPU has the following main working nodes:

• AC input
• input noise suppression LC – filters
• rectifier (diode bridge)
• PFC circuit
• line filter capacitor
• additional power supply 12 V
• power supply of fans for forced cooling
• PWM controller circuit
• synchronous rectifier and its control circuit
• PIC controller control circuit
• feedback regulator circuit
• DC main voltage output

The ASIC power supply installer needs:

• study the structure and principle of its operation
• have a schematic diagram
• purchase the appropriate equipment
• master the algorithm for correct diagnosis

During the diagnostics of the APW8 UPS, you must:

• check the passage of AC mains voltage to the input of the diode bridge
• in the absence of U in the input circuits, eliminate the malfunction
• make sure there is no short circuit after the diode bridge
• check the PFC transistor and its driver
• check the 12 V auxiliary circuit, if it is absent, eliminate the cause according to the circuit diagram
• check the operation of the main PWM controller, its control circuits
• make sure that the PIC controller chip, synchronous rectifier is working
• check overload protection, rectifier synchronous filter, DC output circuits

After maintenance and troubleshooting, any UPS should operate for 2 hours at a rated load of 80%. If the ASIC PSU has worked stably, the repair can be considered complete.

Specifications APW8

Original power supply unit APW8 released by BITMAIN

Dimensions – 20 x 15.7 x 4.2 cm

Power – 1.85 kW

Weight (packed) – 1.7 kg

Noise level – 67 dB

Constant output U – 12 V

Auxiliary power supply rated current – up to 5 A

Maximum output current of the main source – up to 110 A

Rated input U – 220 V

Conclusions

• The ASIC power supply is a complex technical device. The performance of the load connected to it depends on the stable operation of which: hash cards, video cards, motherboards of rigs.
• Having mastered the repair of APW8, the service center gets an advantage over other services for the repair of mining equipment, since the vast majority of masters are engaged in repairing only hashboards and control boards.
• Structural, as well as schematic diagrams of most ASIC power supplies are similar to each other. Therefore, having learned how to repair PSU APW8, it will be easy to understand how to restore other UPSs.