This maintenance guide provides comprehensive instructions on how to maintain an Antminer L7 properly. We will cover routine testing, locating faulty chips, re-soldering and replacing parts, making relevant maintenance/analysis records, assembling the machine for aging tests and more. This guide is designed to help you make sure your Antminer L7 is running at its optimal performance level with minimal downtime. Following the steps outlined in this guide will ensure that your miner remains in good condition for years.
Preparation and Maintenance Guidelines
It’s essential to take the time to properly prepare and maintain components before, during, and after installation. This includes applying thermal gel for better heat transfer, forming air ducts for better airflow, connecting power supplies in the correct sequence, fixing chips to prevent overheating, and ensuring test fixtures meet production requirements. Additionally, these guidelines should also include instructions on cleaning components with approved solvents such as isopropyl alcohol or distilled water, as well as how to store components away from extreme temperatures and humidity levels safely. Finally, regularly scheduled maintenance checks should be carried out every few months or at least annually to guarantee the proper functioning of all parts within the system.
Preparation Requirements for Repair Platform, Tools, and Equipment
I. Platform Requirements:
- To perform maintenance work, an anti-static maintenance workbench is required. It should be grounded, and an anti-static wristband and grounding are necessary.
II. Equipment Requirements:
- Constant temperature soldering iron (350°C-380°C) with a pointed tip for soldering small patches such as chip resistors and capacitors.
- Hot air guns and BGA rework stations are used for chip / BGA disassembly and welding.
- Multimeter with welded steel pins and heat-shrinkable sleeves for easy measurement. The recommended model is the Fluke 15b+ multimeter.
- Oscilloscope. The recommended model is UTD2102CEX+. A network cable is required for an internet connection and a stable network.
III. Test Tool Requirements:
- ARC Antminer Hashboard Tester
- Lab PSU 10-30V / 1-15A
- APW12 power supply: AP12_12V-15V_V1.2 and power adapter cable. It is recommended to use thick copper wire for the positive and negative poles of the power supply to connect the power supply and the power board and only limited to PT1 and maintenance test use.
- Use the test fixture of the V2.3 control board (test fixture material number ZJ0001000001). The positive and negative poles of the test jig need to be installed with discharge resistors. Using a cement resistance of 20 ohms and 100W or more is recommended.
IV. Maintenance Auxiliary Materials/Tools Requirements:
- Solder Paste 138°C, flux, Mechanic lead-free circuit board cleaner, and anhydrous alcohol.
- Mechanic lead-free circuit board cleaner cleans up the flux residue after maintenance.
- Thermally conductive gel is used to apply to the chip surface after repair.
- Ball-planting steel mesh, desoldering wick, and solder balls (the recommended ball diameter is 0.4mm).
- When replacing a new chip, it is necessary to tin the chip pins and then solder them to the hash board. Apply thermally conductive gel evenly on the chip’s surface, then lock the heatsink.
- Serial port code scanner.
- Serial port adapter board RS232 to TTL adapter board 3.3V.
- Self-made short-circuit probe (use the pins for wiring and welding and heat the shrinkable sleeve to prevent short-circuit between the probe and the small heatsink).
V. Common Maintenance Spare Material Requirements:
- 0402 resistor (0R, 10K, 4.7K,)
- 0402 capacitor (0.1uF, 1uF)
- When replacing a chip, pay attention to the operation method. After replacing any component, check that the PCB board has no obvious deformation. Check the replacement and surrounding parts for missing parts, open circuits, and short circuits.
- Maintenance personnel must have electronic knowledge, at least one year of maintenance experience, and proficiency in BGA/QFN/LGA packaging and welding technology.
- After repair, the hashboard must be tested more than twice, and all tests must pass.
- Check the tools to ensure that the test fixture can work typically. Determine the parameters of the maintenance station test software, the version of the test jig, and other related parameters.
- To test repairing and replacing the chip, test the chip first and then do the functional test after it passes. The functional test must ensure that the small heatsink is welded correctly, the large heat sink is installed, and the thermal adhesive gel is applied evenly. Two hash boards should be placed simultaneously to form an air duct when using the chassis to dissipate heat. For single-sided testing in production, the air duct must also be formed.
- When measuring the signal, use fans to dissipate heat and ensure the fans are at full speed.
- When powering on the hashboard, connect the negative copper cord of the power supply first, then the positive copper cord of the power supply, and finally, insert the signal cable.
- When disassembling, reverse the order of installation. First, remove the signal cable, then pull the positive copper cord of the power supply, and finally, remove the negative copper cord of the power supply. If you do not follow this order, it may cause damage to U1 and U2.
- Before testing the pattern, the repaired hashboard must cool down before testing; otherwise, it will lead to testing NG.
- Pre-tin the chip pins with solder paste to replace a new chip and then solder them to the PCB for repair.
Overview of Antminer L7 Components
L7 Hashboard Structure:
The L7 hash board is made up of 120 BM1489 chips, divided into 24 domains, each consisting of 5 ASIC chips. The BM1489 chips run on a working voltage of 0.6V. The 24th to 21st domains are powered by the 19.6V output from the boost circuit U13 to the LDOs (U249, U247, U243, U239), which output 1.8V and 0.8V. The power supply for the 20th domain LDO is 14.4V, which outputs 1.8V and 0.8V, reducing the domain voltage by 0.6V with each subsequent domain.