Antminer S19j Pro Maintenance & Repair Guide

Introduction

The Bitmain Antminer S19j Pro is one of the most widely deployed Bitcoin miners in the world — and for good reason. Delivering approximately 104 TH/s of SHA-256 hashrate at around 3068 W, the S19j Pro hit the sweet spot between performance and cost when it launched in 2021, and it remains a workhorse in home mining operations and hosting facilities alike. If you are running one of these machines, you are running proven silicon that has earned its reputation through millions of hours of field operation across the globe.

The “j” in S19j stands for Bitmain’s cost-optimized approach to the S19 generation. Where the standard S19 Pro uses approximately 76 BM1398 chips per hashboard, the S19j Pro uses 126 BM1362 chips per hashboard — more chips, each running at lower individual power, achieving comparable total hashrate through sheer parallelism. This is not a lesser design. It is a different engineering philosophy: more transistors doing less work each, running cooler individually, with the tradeoff being a higher total chip count that demands more attention during maintenance and repair. Understanding this distinction is critical because it affects every diagnostic and repair procedure in this guide.

This guide is your complete field manual for keeping the Antminer S19j Pro running at peak performance. We cover routine maintenance that prevents problems before they start, diagnostics that pinpoint exactly what went wrong, and repair procedures that get you back to hashing. Whether you are a home miner running a single unit as a Bitcoin space heater or an operator managing dozens in a hosting facility, this guide gives you the knowledge to maintain your hardware like a professional.

Technical Specifications

Before you pick up a screwdriver, know your hardware. The S19j Pro shares the S19-generation chassis design but uses a fundamentally different chip — the BM1362 instead of the BM1398. This means different voltage domains, different chip counts, different signal paths, and different repair considerations. Do not assume S19 Pro procedures apply directly to the S19j Pro.

S19j Pro vs. S19 Pro — Key Differences

These two miners share a name and a generation, but they are different machines at the board level. This comparison matters because repair guides for one do not fully apply to the other:

The practical implication: the S19j Pro has nearly twice as many chips to inspect, diagnose, and potentially repair. Each voltage domain runs at a lower voltage, making precise measurement even more important. The signal chain is longer (126 chips in series), so a single failed chip earlier in the chain can take out all downstream chips from detection.

Before You Begin

Safety Warnings

Summary of safety rules:

1. Power off and unplug before any maintenance. Wait 5 minutes for capacitor discharge.
2. Wear an ESD wrist strap grounded to the miner chassis whenever handling hashboards.
3. Let the miner cool for 10+ minutes after shutdown before touching heatsinks.
4. Work in a clean, dry environment — no liquids near the miner, no metal shavings, no conductive debris.
5. Never operate the miner with the cover removed — airflow direction is critical for cooling all four hashboards.
6. Follow the power connection sequence — negative first on, negative last off.
7. Document everything — photograph cable positions and connector orientations before disconnecting anything.

Routine Maintenance

Prevention is cheaper than repair. A disciplined maintenance schedule extends the life of your S19j Pro, maintains peak hashrate, and prevents the catastrophic failures that turn a profitable miner into a paperweight. The BM1362 chips are designed for years of continuous operation — but only if you give them clean air, proper cooling, and stable power. With 504 chips across four boards, the S19j Pro has more individual points of potential failure than its 3-board siblings, making preventive maintenance even more valuable.

Recommended Maintenance Schedule

Visual Inspection

Start every maintenance session with a visual once-over. You are looking for the early warning signs of problems that will become expensive if ignored:

• Dust accumulation — The S19j Pro moves a massive volume of air through four hashboards stacked in the chassis. Dust accumulates on fan blades, heatsink fins, and the intake grill. Heavy dust buildup restricts airflow, raises chip temperatures, and forces fans to spin faster (louder and shorter lifespan). In dusty environments (garages, basements, workshops), cleaning frequency should double.
• Discoloration on hashboards — Brown or yellow discoloration around components indicates overheating. This is a red flag that demands immediate investigation. Check for blocked airflow, failed fans, or degraded thermal gel.
• Corrosion on connectors — Green or white residue on power connectors, cable pins, or the Ethernet port indicates moisture exposure. Clean with IPA and assess your operating environment’s humidity.
• Physical damage — Bent heatsink fins, cracked PCB traces, loose screws, or damaged fan blades. Shipping damage is common — always inspect a new or relocated unit before powering on.
• Cable condition — Check the flat ribbon cables connecting all four hashboards to the control board. These are fragile. A cable that has been pinched, bent sharply, or pulled can cause intermittent hashboard detection failures. With four boards, that is four cables to inspect.
• PSU inspection — Look at the APW12’s input and output cables for fraying, heat damage, or loose connections. The power connector should seat firmly without play.
• PCB deformation — Check each hashboard for bowing or warping. PCB deformation can cause poor thermal contact between chips and the heatsink, leading to hot spots and chip degradation.

Cleaning Procedures

Dust is the number one enemy of air-cooled miners. The S19j Pro’s four fans pull air through the chassis at high velocity — and they pull in everything floating in that air. Here is how to clean properly:

External Cleaning (Monthly)

1. Power off and unplug the miner. Wait 5 minutes.
2. Use compressed air to blow dust from the intake side (fan side) — blow from outside in, then from inside out to dislodge deep buildup.
3. Clean the exhaust side similarly.
4. Hold each fan blade still while blowing — letting fans spin freely under compressed air can damage bearings or generate back-EMF into the control board.
5. Wipe the exterior chassis with a dry, lint-free cloth.

Internal Deep Clean (Quarterly)

1. Power off, unplug, and wait 10 minutes for cooling and capacitor discharge.
2. Remove the top cover screws (Phillips #2) and lift the cover.
3. Put on your ESD wrist strap and clip it to the metal chassis.
4. Photograph the interior before touching anything — this is your reference for reassembly.
5. Use compressed air in short bursts (2–3 seconds) to blow dust from:
   • Heatsink fin arrays (blow perpendicular to fins to clear channels)
   • Between all four hashboards — the middle boards tend to accumulate more dust
   • Control board components
   • All cable connectors and sockets
6. Use a soft anti-static brush to gently dislodge any caked-on dust that compressed air cannot remove.
7. Inspect the heatsink mounting on all four boards — ensure heatsink clips or screws are tight and the heatsink sits flush against the chips. Any gap means thermal gel failure.
8. Reassemble in reverse order. Ensure the top cover is properly seated — the airflow path through the S19j Pro depends on the enclosure being sealed to form proper air ducts.

Thermal Gel Replacement

The S19j Pro uses thermally conductive gel between the BM1362 chips and the aluminum heatsinks to transfer heat. Over time — typically 12–18 months of continuous operation — this thermal interface degrades: it dries out, develops micro-cracks, and loses conductivity. The result is rising chip temperatures even when airflow is perfect.

Signs that thermal gel needs replacement:

• Chip temperatures consistently 5–10°C higher than when new (same ambient temperature and fan speed)
• Thermal throttling despite adequate airflow
• Individual chips running significantly hotter than neighbors on the same hashboard
• Visual inspection reveals dried, cracked, or unevenly distributed gel

Thermal gel replacement procedure:

1. Power off, unplug, wait 10 minutes, ESD strap on.
2. Remove top cover and carefully detach the heatsink(s) from the hashboard. Do not pry. If the heatsink is stuck to dried gel, gently twist while pulling straight up.
3. Clean old gel from both the chip surfaces and the heatsink contact surface using 99% isopropyl alcohol and lint-free cloths. Use lead-free circuit board cleaner for stubborn residue. Ensure no residue remains.
4. Apply fresh thermal conductive gel to each chip. The S19j Pro has 126 chips per hashboard — apply gel evenly across each chip surface. Uniform thickness is critical for consistent heat transfer across all chips.
5. Reseat the heatsink carefully. Apply even pressure — do not tighten one corner first. Use a diagonal tightening pattern for screws.
6. Repeat for all hashboards that need service. With four hashboards, plan for this to take considerably longer than a 3-board machine.
7. After reassembly, power on and monitor chip temperatures for the first 30 minutes. You should see a noticeable drop — typically 5–15°C improvement.

Fan Maintenance

The S19j Pro runs four fans — two intake, two exhaust. These fans are the first line of defense against thermal damage. When fans degrade, everything downstream suffers, and with four hashboards generating heat, cooling capacity cannot be compromised.

Fan health checks:

• Listen: Healthy fans produce a consistent high-pitched whine. Grinding, clicking, rattling, or intermittent speed changes indicate bearing wear.
• Watch: All four fans should spin at similar speeds. A visually slower fan is failing.
• Monitor: Check fan RPM in the miner dashboard. Healthy fans typically run between 4000–6000 RPM depending on load and ambient temperature. A fan consistently below 3000 RPM under load is failing.
• Clean: Dust buildup on fan blades creates imbalance. This accelerates bearing wear and increases noise. Clean fan blades monthly.

Fan replacement indicators:

• Fan RPM drops below minimum threshold and triggers fan lost or fan speed error in logs
• Visible wobble or vibration during operation
• Fan does not spin up on power-on
• Bearing noise audible above normal operating noise

Diagnostics & Troubleshooting

When something goes wrong, you need data — not guesses. The S19j Pro provides multiple diagnostic channels: LED indicators, the web dashboard, kernel logs via SSH, and the miner API. Here is how to use all of them.

LED Status Indicators

The S19j Pro control board has LED indicators that give immediate visual feedback on the miner’s state:

Startup sequence (normal): On power-on, both the fault (red) and running (green) LEDs light simultaneously during initialization. After initialization, the red light flashes while the miner connects to the mining pool. Once the pool connection is established, the red light turns off, the green light becomes steady, and hashrate appears in the dashboard. This full sequence typically takes 3–5 minutes. With four hashboards initializing, the S19j Pro may take slightly longer than 3-board models.

Web Dashboard Diagnostics

Access the S19j Pro’s web interface by navigating to the miner’s IP address in your browser. Default login credentials are root / root (change these immediately on first setup).

Key dashboard sections to check:

• Miner Status: Shows real-time hashrate per hashboard, total hashrate, and pool connection status. All 4 chains should show approximately 26 TH/s each for a combined ~104 TH/s.
• Hardware Status: Displays chip count per hashboard (should be 126 on each), PCB temperature, and chip temperature per board.
• Fan Status: RPM readings for all 4 fans. Look for significant variance between fans.
• Pool Status: Shows configured pools, accepted/rejected shares, and stale rates. A reject rate above 2% warrants investigation.
• System Log: The kernel log accessible from the web interface — same data you get via SSH, just less convenient for filtering.

SSH Diagnostic Commands

SSH gives you the deepest access to the S19j Pro’s diagnostics. These commands are your scalpel when the dashboard is too blunt.

# Connect via SSH (default credentials: root / root)
ssh root@MINER_IP_ADDRESS

# View the full kernel log (hardware events, errors, chain init)
dmesg

# View miner-specific log
cat /tmp/log/bmminer.log

# Filter for errors only
cat /tmp/log/bmminer.log | grep -i "error|fault|fail"

# Check hashboard chain status (look for all 4 chains)
cat /tmp/log/bmminer.log | grep -i "chain"

# Check chip detection per chain (should show 126 on each)
cat /tmp/log/bmminer.log | grep -i "chips"

# View system uptime and load
uptime

# Check network connectivity
ping -c 4 8.8.8.8

# DNS resolution test (use your pool's hostname)
nslookup stratum.braiins.com

# Check fan speeds (if accessible via sysfs)
cat /sys/class/hwmon/hwmon*/fan*_input

# View temperature sensors
cat /sys/class/hwmon/hwmon*/temp*_input

# Check running mining process
ps | grep -i "bmminer|cgminer"

# View system memory usage
free -m

# Check disk/flash usage
df -h

# Query miner summary from another machine on the same network
# Replace MINER_IP with your S19j Pro's IP address

# Get overall mining summary (hashrate, accepted, rejected, uptime)
echo '{"command":"summary"}' | nc MINER_IP 4028

# Get per-device (hashboard) stats — expect 4 devices
echo '{"command":"devs"}' | nc MINER_IP 4028

# Get pool connection status
echo '{"command":"pools"}' | nc MINER_IP 4028

# Get detailed stats (temperature, fan speeds, chip counts)
echo '{"command":"stats"}' | nc MINER_IP 4028

Common Error Codes & Messages

Here are the most frequent error messages you will encounter on the S19j Pro, what they mean, and how to fix them. For a comprehensive reference covering all Antminer models, see our Antminer Error Code & LED Reference Guide.

Hashboard Testing

When you suspect a specific hashboard, isolate it systematically:

1. Identify the problematic board — the web dashboard shows per-chain hashrate and chip count. A board with 0 TH/s or fewer than 126 chips is your suspect.
2. Reseat the flat cable — power off, disconnect and reconnect the ribbon cable between the suspect hashboard and the control board. These connectors can work loose over time.
3. Swap the cable position — connect the suspect hashboard to a different port on the control board. If the problem follows the hashboard, the hashboard is faulty. If the problem stays at the same port, the control board port may be faulty.
4. Visual inspection — remove the hashboard and inspect under good lighting. Look for:
   • Burn marks or discoloration around chips or voltage regulators
   • Cracked solder joints (especially around connector pins)
   • Swollen or leaking capacitors
   • Physical damage to PCB traces
   • Scorching or collision offset parts
   • Missing components
5. Impedance test — use a multimeter to test the impedance of each voltage domain. This detects short circuits or open circuits before you apply power. The voltage of each domain should be approximately 0.32V.
6. Voltage domain check — with a lab PSU or the APW12, measure the voltage output across each chip group. Absent or wildly off voltage indicates power delivery issues on the hashboard.

Understanding the S19j Pro Hashboard

Before diving into specific repair procedures, you need to understand the S19j Pro hashboard architecture. This knowledge separates effective troubleshooting from guesswork.

Hashboard Architecture

Each S19j Pro hashboard contains 126 BM1362 chips organized into 42 groups of 3 chips each. The operating voltage per chip domain is approximately 0.32V. Here is how the power delivery works:

• Groups 1–35: Powered by the main 15V supply, stepped down through voltage regulators to produce the 0.32V per domain.
• Groups 36–42 (7 groups): Powered by the boost circuit (U238), which raises the 15V PSU input to 20V, then provides LDO power for each of these groups.
• Group 35: Supplied directly by VDD 15V, with 0.32V derived by reducing the voltage for each domain.

This two-tier power architecture means that a boost circuit failure will knock out groups 36–42 (21 chips) while leaving the other 105 chips operational. You will see this pattern in the logs as a partial chip count — roughly 105 out of 126 chips detected.

Signal Flow Through the BM1362 Chain

Understanding signal flow is essential for locating faulty chips. The S19j Pro uses five main signal paths through the 126-chip chain:

Key diagnostic insight: Except for RX, all signals flow forward. If a chip fails in the middle of the chain, all downstream chips lose their signal. This is why a single bad chip at position 40 can cause the miner to report only 40 chips detected instead of 126. The RX signal flows backward, so an RX problem at chip 60 means chip 0 through 59 lose their return communication path.

Boost Circuit

The boost circuit is a critical component that raises the 15V power supply input to 20V. This boosted voltage powers groups 36–42. You can verify the boost circuit by measuring voltage across C915 — it should read approximately 20V. If it reads significantly lower or zero, the boost circuit has failed and those 21 chips (7 groups × 3 chips) will not function.

Common Repairs

Some repairs are within reach of a competent home miner with basic tools. Others require BGA rework stations, oscilloscopes, and years of board-level repair experience. We will be honest about that line — crossing it without the skills risks making a repairable board unrepairable.

Fan Replacement

Fan replacement is the most common S19j Pro repair and the most approachable for DIY. The S19j Pro uses four high-speed fans — two on the intake side and two on the exhaust side.

Procedure:

1. Power off and unplug. Wait 5 minutes.
2. Remove the fan guard screws on the affected side (Phillips #2).
3. Disconnect the fan power cable from the control board header. Note the connector orientation — photograph first.
4. Remove the fan from the chassis.
5. Install the replacement fan with the airflow direction matching the original (arrow on fan housing indicates airflow direction). Intake fans blow INTO the chassis; exhaust fans blow OUT.
6. Reconnect the fan power cable to the correct header on the control board.
7. Secure the fan guard.
8. Power on and verify the new fan appears in the dashboard with a healthy RPM reading.

Power Supply Issues

The S19j Pro uses the APW12 power supply (12V–15V output). Power delivery problems can manifest as no startup, missing hashboards, low hashrate, or random shutdowns.

APW12 diagnostics:

• No LED on PSU: Check wall outlet voltage (200–240V AC required), check power cord for damage, check PSU fuse.
• PSU LED on but miner does not start: Verify DC output voltage with a multimeter — should read 12–15V DC. Check the power cable connection to the miner chassis.
• Miner starts but hashboards intermittent: Under load, the APW12 must deliver stable current to all four hashboards. A failing PSU may sag under load. Measure voltage while running (carefully, with the cover on and using accessible test points).
• Voltage out of range: If the APW12 output drifts outside the 12–15V range, the miner may produce errors or fail to initialize hashboards. The PSU may need replacement.

Hashboard Repair

Hashboard repair on the S19j Pro is more involved than on many other Antminer models due to the high chip count (126 per board) and tight component spacing. Here are the most common scenarios.

Scenario 1: Zero Chips Detected (ASICNG with 0 chips)

When the test fixture or miner log shows zero chips on a hashboard, work through this sequence:

1. Check the power supply output — verify the PSU is delivering correct voltage to the hashboard. Look for short circuits in the MOS transistors by measuring resistance between pins 1, 4, and 8.
2. Check voltage domain output — each domain should show approximately 0.32V. If the power supply shows 15V at the input but no domain voltage is present, the problem is in the power distribution circuitry on the board.
3. Check the PIC circuit — measure the output on pin 2 of U6. It should read approximately 3.3V. If there is no 3.3V output, check the test fixture cable connection to the hashboard and reprogram the PIC chip.
4. Check the boost circuit — measure voltage across C915. Should be approximately 20V. If significantly lower or zero, the boost circuit (U238) has failed.
5. Check LDO 1.2V and PLL 0.8V outputs — probe each LDO and PLL output pin with a multimeter (negative lead on GND). LDO should read ~1.2V, PLL should read ~0.8V. Deviations indicate failed regulators or short-circuited filter capacitors.
6. Check chip signals — measure CLK, CI, RI, BO, and RST at the test points between chips, comparing against the expected voltage values from the signal flow table above. Significant deviations from adjacent groups point to the faulty area.

Scenario 2: Incomplete Chip Detection (ASICNG with X chips, or ASIC113)

When the hashboard detects some but not all 126 chips, the problem is typically a single failed chip breaking the signal chain:

• ASICNG (X): If the display shows “ASICNG” followed by a number in parentheses, that number identifies the chip position where the chain breaks. Check the CLK, CI, and BO resistors on the front and back of the Xth chip. Check for cold solder joints on the chip itself. Among the 3 chips in that domain group, inspect for abnormal pin soldering.
• ASIC113 (or similar partial count): The board finds most chips at low baud rate (115200) but misses some at high baud rate (12M). Use the binary search method (dichotomy) to isolate the faulty chip:
  1. Short-circuit the RO test point and 1V2 test point between chip 63 and chip 64 (midpoint).
  2. Run the detection software. If 63 chips are found, the first half is good.
  3. Move the short-circuit probe to the midpoint of the second half (chip 95).
  4. Continue halving until the specific faulty chip is identified.
  5. Inspect the chip visually. If appearance is normal, replace it anyway — BM1362 chips can be internally damaged with no visible external signs.

Scenario 3: Pattern NG (Nonce Response Data Incomplete)

When the PT2 station reports Pattern NG, it means one or more chips are returning corrupted or incomplete nonce data. The chip is detected but not functioning correctly:

• Examine the test log for chips with significantly lower response rates compared to others in the same domain.
• Domain and ASIC numbers start from 0 in the logs.
• If a group of chips (e.g., ASIC [57], [58], [61], [63], [64]) show low response rates, replace the chip with the lowest response rate in that domain group first.
• If the chip appearance is not visibly damaged, this typically indicates internal silicon degradation. Replacement is the only fix.

Scenario 4: PT2 Function Test Serial Port Does Not Stop (Long-Running)

If the chip test (PT1) passes but the PT2 function test enters an endless loop:

1. Monitor the serial port print log during the PT2 test.
2. When the long-running condition begins, use a short-circuit probe to short RO and 1.2V starting from the first chip.
3. If the serial port stops long-running after the short, the first chip is okay. Move to the next chip.
4. The chip that, when shorted, does NOT stop the long-running condition is the faulty chip.
5. This failure is almost always a damaged chip. Replace it.

Scenario 5: PT1 OK but PT2 Consistently Reports Chip X as NG

When a specific chip repeatedly fails the functional test despite passing the initial chip test:

• Inspect the physical appearance of the chip and its soldering quality.
• Measure the capacitor and resistor values adjacent to the chip.
• The most common causes are: poor chip soldering (cold joints), damaged capacitors or resistors in the chip’s domain, or abnormal resistance values in the supporting components.
• Re-flow the chip first (add flux around the chip, heat to dissolve state to allow solder to re-wet). If the fault persists after re-flow, replace the BM1362 chip.

BM1362 Chip Replacement Procedure

For those with the required skills and equipment, here is the BM1362 replacement procedure:

1. Pre-tin the replacement chip — apply solder paste (138°C) to the new BM1362 chip pins before placing it on the board. This ensures proper solder contact on all pads.
2. Remove the faulty chip — use the hot air rework station to heat the chip evenly until the solder melts. Lift straight up. Do not twist or rock the chip.
3. Clean the pads — use desoldering wick and flux to clean the PCB pads. Inspect under magnification for lifted or damaged pads.
4. Place and solder the new chip — align the pre-tinned chip on the cleaned pads. Apply heat evenly with the rework station. Allow the solder to flow naturally.
5. Post-soldering inspection — check that the PCB has no visible deformation. Verify the replacement chip and all surrounding components for missing parts, open circuits, or short circuits.
6. Apply thermal gel — apply thermally conductive gel evenly on the chip surface, then lock the heatsink in place.
7. Cool and test — let the repaired hashboard cool completely before testing. A hot board will produce false NG results.
8. Test twice — the repaired hashboard must pass the test fixture at least two times. After the first pass, set the board aside to cool for a few minutes, then test again. Both tests must pass for the repair to be considered successful.

Network & Control Board Issues

The control board is the brain of the S19j Pro — it communicates with all four hashboards, manages fan speeds, connects to the pool, and runs the firmware.

Common control board problems:

• IP not detected on network: Check the Ethernet cable (try a different cable). Verify the IP scanner is scanning the correct subnet. Try a direct connection to your router. If the control board LED shows no network activity, the Ethernet port or control board may be faulty.
• Missing chain (less hashboards than expected): If one of the four hashboard chains disappears from the dashboard, first check the physical connection between the hashboard ribbon cable and the control board port. If the connection is solid, swap the ribbon cable with a known-good one. If the chain still does not appear, test the hashboard standalone with PT2 — if it passes, the control board port is likely the issue.
• Random reboots or freezes: Often caused by corrupted firmware, marginal power delivery to the control board, or overheating. Try a firmware re-flash first. If the problem persists, the control board may need replacement.
• Fan display abnormal: Verify that the fans are physically spinning and connected properly. Check the control board fan headers for bent or broken pins. If the fans work but the dashboard shows abnormal readings, the control board sensor circuit may be faulty.

Temperature Sensor Troubleshooting

The S19j Pro uses four temperature sensors on each hashboard (U5, U7, U8, U9) to monitor chip temperatures. These sensors are located on the back of the PCB, while their matching resistors are on both the front and back. Temperature anomalies can cause shutdowns, throttling, or false alarms.

When the test fixture reports “PIC sensor NG” or abnormal temperature:

1. Check whether the four resistors R217, R218, C22, C23 are soldered properly.
2. Verify the soldering of the PIC chip U5 pins — cold joints here are common.
3. Inspect all four temperature sensors and their matching resistors:
   • Sensor 1: U5 with R216, R219, R220
   • Sensor 2: U7 with R221, R223
   • Sensor 3: U8 with R224, R226
   • Sensor 4: U9 with R229–R231
4. Verify the 3.3V power supply to the temperature sensor circuit is present and stable.
5. Check the soldering quality of the chip that connects the sensor to the small heatsink — poor thermal contact here causes inaccurate readings.
6. Inspect the large heatsink for deformation — a warped heatsink can cause poor chip heat dissipation, resulting in real temperature differences that the sensors correctly report as abnormal.

Firmware & Software

Firmware Updates

Bitmain periodically releases firmware updates for the S19j Pro that can fix bugs, improve stability, and sometimes increase efficiency. Here is how to handle firmware responsibly:

• Check current firmware version via the web dashboard (System > Firmware Version) or SSH (cat /etc/bitmain-release).
• Download firmware only from official sources — Bitmain’s official website or verified community sources. Malicious firmware is a real attack vector in Bitcoin mining — compromised firmware can redirect a portion of your hashrate to an attacker’s pool without you noticing.
• Back up your configuration before updating — pool settings, network configuration, and any custom overclocking/underclocking profiles.
• Never interrupt a firmware update — if you see a green fast-blinking LED, the miner is actively writing firmware. Power loss during this process can brick the control board.
• Test after updating — verify all four hashboards are detected, chip counts are at 126 each, and hashrate returns to normal within 10 minutes of reboot.

Alternative Firmware Options

The S19j Pro is compatible with several third-party firmware options that offer features beyond Bitmain’s stock firmware:

• BraiinsOS+ — Open-source firmware with autotuning that optimizes each chip individually for maximum efficiency. Supports both underclocking (lower power, quieter, great for home mining) and overclocking. If you want to run your S19j Pro as a quiet space heater at reduced power, BraiinsOS+ with underclocking is the way to do it.
• LuxOS — Another third-party firmware option with advanced tuning features and fleet management capabilities.
• Vnish — Popular aftermarket firmware with aggressive tuning profiles for maximizing hashrate.

Configuration Best Practices

• Change default credentials immediately — the default root / root is an open invitation. Set a strong password.
• Configure multiple pool addresses — set Pool 1, Pool 2, and Pool 3 for failover. If your primary pool goes down, the miner automatically switches to the next. This prevents hash rate downtime.
• Set appropriate fan speed profiles — if your firmware supports it, configure fan speeds that balance noise and cooling for your environment. For home mining, running at a fixed 60–70% fan speed with underclocked hashrate is a common approach.
• Enable network monitoring — configure email or webhook alerts for hashrate drops, temperature warnings, or hashboard disconnections. Catching problems early saves money.
• Document your settings — screenshot or export your pool configuration, network settings, and tuning profiles. If you need to re-flash firmware, having your settings documented saves time.

Whole-Miner Troubleshooting

Some problems manifest at the whole-miner level rather than on an individual hashboard. Here is how to diagnose the most common full-system failures:

Maintenance & Repair Flowchart

When a hashboard fails, follow this systematic approach to avoid wasted time and unnecessary component replacements:

1. Routine Inspection
   • Visually inspect the board for PCB deformation, scorching, burnt marks, collision offset parts, or missing components.
   • Test the impedance of each voltage domain to detect short circuits or open circuits.
   • Each domain voltage should be approximately 0.32V.
2. Chip Test (PT1)
   • Use the hashboard test fixture to identify how many chips are detected.
   • The test fixture LCD/log will report the chip count and any specific error codes.
3. Locate the Faulty Chip
   • Based on the test result, check the test points (CO, NRST, RO, XIN, BI) and voltages (VDD0V8, VDD1V2) near the reported fault position.
   • Remember: CLK, CO, BO, and RST are forward signals. RX is the only backward signal. An abnormal fault point can be found by following the signal direction.
4. Repair
   • Try re-soldering first: add flux around the chip, heat to dissolve state, and allow solder to re-flow.
   • If re-soldering does not fix the issue, replace the BM1362 chip.
5. Verify
   • After repair, let the board cool completely.
   • Test at least twice on the test fixture. Both tests must pass.
   • For the first test after chip replacement, cooling is especially important — a hot board produces false NG results.

Frequently Asked Questions

When to Call a Professional

This guide covers a lot of ground, but there is a clear line between what you should attempt and what requires professional intervention. Here is an honest assessment:

DIY-appropriate tasks:

• All routine maintenance (cleaning, visual inspection, thermal gel replacement)
• Fan replacement
• Ribbon cable troubleshooting and replacement
• Firmware updates and configuration
• PSU swaps
• Control board replacement
• Basic diagnostics via dashboard and SSH

Professional repair required:

• BM1362 chip replacement (BGA rework)
• EEPROM reprogramming or replacement
• PIC chip failures
• Boost circuit repair
• Damaged PCB traces
• Multiple chip failures on a single board
• Voltage regulator failures
• Any repair requiring an oscilloscope for signal tracing

The S19j Pro’s 126 chips per board make professional repair especially valuable. A board-level technician with the right equipment can diagnose and fix a specific chip failure in an hour. An amateur attempting the same repair without experience can turn a $50 fix into a destroyed $300+ hashboard. Know your limits.

Interactive Hashboard Schematic

Explore the ANTMINER S19J PRO hashboard layout below. Toggle layers to isolate voltage domains, signal chains, test points, key components, and thermal zones. Hover over any region for quick specs — click for detailed diagnostics, failure modes, and repair guidance.