Antminer S19k Pro Maintenance & Repair Guide

Introduction

The Bitmain Antminer S19k Pro is one of the most refined miners in the entire S19 generation — and one of the most underestimated. Delivering approximately 120 TH/s of SHA-256 hashrate at around 2760 W, this machine arrived late in the S19 cycle as Bitmain’s efficiency champion, squeezing more terahashes per watt than any of its S19-series siblings. Where earlier S19 variants leaned on raw power consumption or higher chip counts to hit their numbers, the S19k Pro took a different path: the BM1366BS — the same advanced 5nm-class ASIC chip that powers the S19 XP. Fewer chips, lower voltage per domain, and a wall plug efficiency of 23 J/TH that puts it in a different league from the S19 Pro’s 29.5 J/TH.

For the home miner, this efficiency story is everything. The S19k Pro draws about 300W less than a standard S19 Pro while hashing 15% faster. Underclock it with aftermarket firmware and you have a machine that can run at 1200–1800W while delivering 50–80 TH/s — a legitimate space heater that pays for the electricity it consumes. This is exactly the kind of institutional hardware that rewards the mining hacker who knows how to maintain it.

This guide is your complete field manual for keeping the Antminer S19k Pro at peak performance. We cover routine maintenance, deep diagnostics, board-level repair procedures, and firmware optimization. Whether you are running a single S19k Pro as a Bitcoin space heater in your basement or operating a rack of them in a dedicated facility, this guide gives you the knowledge to maximize uptime and extend the lifespan of every component.

Technical Specifications

Before you pick up a screwdriver, know your hardware. The S19k Pro shares the S19-generation chassis and form factor but uses a fundamentally different chip — the BM1366BS instead of the BM1398 (S19 Pro) or BM1362 (S19j Pro). This means different voltage domains, different chip counts per board, different signal characteristics, and different repair considerations. Do not assume that S19 Pro or S19j Pro procedures apply directly to the S19k Pro.

S19k Pro vs. S19 Pro vs. S19j Pro — Key Differences

The S19k Pro, S19 Pro, and S19j Pro share a name and generation but are substantially different machines at the board level. This comparison matters because repair guides and replacement parts are not interchangeable:

The practical implications for maintenance and repair: the S19k Pro uses advanced 5nm chips that are more power-efficient but also more sensitive to ESD, thermal stress, and voltage fluctuations than the older 7nm and 8nm chips. The 4-pin square fan connector is different from the 6-pin connector used by the S19 Pro and S19j Pro — fans are not interchangeable. The CVITEK C97 control board uses different firmware from the Xilinx C52 boards. In short, the S19k Pro is its own machine and requires its own parts and procedures.

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 in the correct sequence.
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. Every time. A disciplined maintenance schedule extends the life of your S19k Pro, maintains peak hashrate, and prevents the catastrophic failures that turn a profitable miner into scrap metal. The BM1366BS chips are designed for years of continuous operation — but only if you give them clean air, proper cooling, and stable power. The S19k Pro’s 5nm chips are more power-efficient than their predecessors, but they are also less forgiving of thermal abuse. Preventive maintenance is not optional on this machine.

Recommended Maintenance Schedule

Visual Inspection

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

• Dust accumulation — The S19k 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 buildup restricts airflow, raises chip temperatures, and forces fans to compensate with higher RPMs — which means louder operation and shorter fan 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. On the S19k Pro’s 5nm chips, thermal damage accumulates faster and is less reversible than on older process nodes.
• Corrosion on connectors — Green or white residue on power connectors, cable pins, or the Ethernet port indicates moisture exposure. Clean with 99% IPA and assess your operating environment. High humidity is the enemy of precision electronics.
• 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.
• Ribbon cable condition — Check the flat ribbon cables connecting all four hashboards to the CVITEK C97 control board. These cables 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 every time.
• 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. Check the PSU fan for smooth operation.
• 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 accelerated chip degradation.

Cleaning Procedures

Dust is the number one enemy of air-cooled miners. The S19k Pro’s four fans pull air through the chassis at high velocity — and they pull in everything floating in that air. Proper cleaning technique matters because careless cleaning can cause as much damage as the dust itself.

External Cleaning (Monthly)

1. Power off and unplug the miner. Wait 5 minutes for capacitor discharge.
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 because they sit in the shadow of the outer boards
   • CVITEK C97 control board components and connectors
   • All ribbon cable connectors and sockets
   • Power connector pins
6. Use a soft anti-static brush to gently dislodge any caked-on dust that compressed air cannot remove. Pay special attention to heatsink fin valleys.
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 visible gap means thermal gel failure and imminent overheating.
8. Check for any loose components, disconnected cables, or signs of corrosion.
9. Reassemble in reverse order. Ensure the top cover is properly seated — the airflow path through the S19k Pro depends on the enclosure being sealed to form proper air ducts across all four hashboards.

Thermal Gel Replacement

The S19k Pro uses thermally conductive gel between the BM1366BS 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. Because the BM1366BS runs on a 5nm process, each chip produces concentrated heat in a smaller die area. Thermal gel degradation hits harder and faster on these advanced chips than on the older 7nm or 8nm parts.

Signs that thermal gel needs replacement:

• Chip temperatures consistently 5–10°C higher than when the miner was new (at the same ambient temperature and fan speed)
• Thermal throttling despite adequate airflow and clean heatsinks
• Individual chips running significantly hotter than their neighbors on the same hashboard
• Visual inspection reveals dried, cracked, or unevenly distributed gel when the heatsink is removed
• The miner has been running continuously for 12+ months without a thermal gel service

Thermal gel replacement procedure:

1. Power off, unplug, wait 10 minutes. Put on your ESD wrist strap.
2. Remove the top cover and carefully detach the heatsink(s) from the hashboard. Do not pry with metal tools. If the heatsink is stuck to dried gel, gently twist while pulling straight up. A plastic spudger can help break the seal without damaging components.
3. Clean old gel from both the chip surfaces and the heatsink contact surface using 99% isopropyl alcohol and lint-free cloths. Use circuit board cleaner for stubborn residue. Ensure absolutely no residue remains on chip surfaces — any contamination reduces thermal transfer.
4. Apply fresh thermal conductive gel to each chip. The S19k Pro has 82 chips per hashboard — apply gel evenly across each chip surface. Uniform thickness is critical. Too much gel actually insulates; too little creates hot spots. Aim for a thin, consistent layer that covers the entire chip surface.
5. Reseat the heatsink carefully. Apply even pressure — do not tighten one corner first. Use a diagonal tightening pattern for mounting screws to distribute pressure evenly across all 82 chips.
6. Repeat for all four hashboards that need service. Budget 30–45 minutes per board.
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 across the board.

Fan Maintenance

The S19k Pro runs four fans — two intake, two exhaust — using a 4-pin square connector. This is a different connector from the 6-pin connector used by the S19 Pro and S19j Pro, so fans are not interchangeable between models. These fans are the first line of defense against thermal damage, and with four hashboards generating heat simultaneously, 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. With four fans running, isolating a noisy fan can be tricky — briefly hold each fan still (one at a time, machine powered off) and spin it by hand to check for bearing roughness.
• Watch: All four fans should spin at similar speeds during operation. A visibly 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 and needs replacement.
• Clean: Dust buildup on fan blades creates imbalance, accelerates bearing wear, and increases noise. Clean fan blades monthly — hold blades still while cleaning.

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 clearly audible above normal operating noise
• Chip temperatures climbing despite clean heatsinks (degraded fan output)

Diagnostics & Troubleshooting

When something goes wrong, you need data — not guesses. The S19k Pro provides multiple diagnostic channels: LED indicators on the control board, the web dashboard, kernel logs via SSH, and the miner API. Here is how to use all of them systematically.

LED Status Indicators

The S19k Pro’s CVITEK C97 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 and hashboards are hashing, the red light turns off, the green light becomes steady, and hashrate appears in the dashboard. This full sequence typically takes 3–5 minutes. The CVITEK C97 board may take slightly longer to initialize than the older Xilinx C52 boards used in earlier S19 models.

Web Dashboard Diagnostics

Access the S19k 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 — leaving default credentials is a security risk on any network-connected device).

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 30 TH/s each for a combined ~120 TH/s.
• Hardware Status: Displays chip count per hashboard (should be 82 on each), PCB temperature, and chip temperature per board. Any board showing fewer than 82 chips needs investigation.
• Fan Status: RPM readings for all 4 fans. Look for significant variance between fans — a fan running 1000+ RPM below its neighbors is likely degrading.
• Pool Status: Shows configured pools, accepted/rejected shares, and stale rates. A reject rate above 2% warrants investigation of network connectivity or pool configuration.
• System Log: The kernel log accessible from the web interface — useful for quick checks, but SSH gives you better filtering capability.

SSH Diagnostic Commands

SSH gives you the deepest access to the S19k Pro’s diagnostics. These commands are your scalpel when the dashboard’s broad overview is not enough.

# 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 82 on each)
cat /tmp/log/bmminer.log | grep -i "chips"

# Check fan speed readings
cat /tmp/log/bmminer.log | grep -i "fan"

# 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 2>/dev/null

# View temperature sensors
cat /sys/class/hwmon/hwmon*/temp*_input 2>/dev/null

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

# View system memory usage
free -m

# Check disk/flash usage
df -h

# Check firmware version
cat /etc/bitmain-release 2>/dev/null || cat /usr/bin/compile_time 2>/dev/null

# Query miner summary from another machine on the same network
# Replace MINER_IP with your S19k 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 per chain)
echo '{"command":"stats"}' | nc MINER_IP 4028

Common Error Codes & Messages

Here are the most frequent error messages you will encounter on the S19k 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 is the problem, isolate it systematically. Do not replace parts until you have confirmed the diagnosis:

1. Identify the problematic board — the web dashboard shows per-chain hashrate and chip count. A board with 0 TH/s or fewer than 82 chips is your suspect. Note the chain number (0–3).
2. Reseat the ribbon cable — power off, disconnect and reconnect the ribbon cable between the suspect hashboard and the control board. These connectors can work loose through vibration over time. Push firmly until the connector clicks.
3. Swap the cable position — connect the suspect hashboard to a different port on the C97 control board. If the problem follows the hashboard, the hashboard is faulty. If the problem stays at the same port, the control board port is the issue.
4. Visual inspection — remove the hashboard and inspect under strong lighting. Look for:
   • Burn marks or discoloration around chips or voltage regulators
   • Cracked solder joints (especially around connector pins and passive components)
   • Swollen or leaking capacitors
   • Physical damage to PCB traces
   • Scorching or misaligned components
   • Missing components — tiny 0402 passives can be knocked loose during shipping or handling
5. Impedance test — use a multimeter to test the impedance of each voltage domain on the hashboard. This detects short circuits or open circuits before you apply power, preventing further damage.
6. Voltage domain check — with a lab PSU or the APW12, measure the voltage output across each chip group. Each domain should show approximately 0.34V. Absent or wildly off voltage indicates power distribution failure on the board.

Understanding the S19k Pro Hashboard

Before diving into specific repair procedures, you need to understand the S19k Pro hashboard architecture. This knowledge separates effective troubleshooting from guesswork, and it separates a successful repair from an expensive mistake.

Hashboard Architecture

Each S19k Pro hashboard contains 82 BM1366BS chips. The BM1366BS is Bitmain’s 5nm-class SHA-256 ASIC — the same chip family used in the S19 XP, optimized for the S19k Pro’s power and thermal envelope. The operating voltage per chip domain is approximately 0.34V. Here is how the power delivery works:

• Main power domain: The majority of chip groups are powered by the main 15V supply from the APW12, stepped down through voltage regulators to produce the ~0.34V per domain.
• Boost circuit domain: A subset of chip groups at the end of the chain are powered by the boost circuit, which raises the 15V PSU input to approximately 18.5V, then provides LDO power for those groups. A boost circuit failure will knock out these downstream chips while leaving the rest operational. You will see this pattern in the logs as a partial chip count — most chips detected, but the last group missing.

This two-tier power architecture means you can quickly narrow down power-related failures: if only the last group of chips is missing, check the boost circuit. If no chips are detected, the problem is upstream in the main power delivery chain.

Signal Flow Through the BM1366BS Chain

Understanding signal flow is essential for locating faulty chips. The S19k Pro uses the same fundamental signal architecture as other BM1366-based boards, with five main signal paths through the 82-chip chain:

Key diagnostic insight: Except for RX, all signals flow forward through the chain. If a chip fails in the middle of the chain, all downstream chips lose their signal and become invisible to the control board. This is why a single bad chip at position 30 can cause the miner to report only 30 chips detected instead of 82. The RX signal flows backward, so an RX problem at chip 50 means chips 0 through 49 lose their return communication path. When troubleshooting, the reported chip count tells you approximately where the chain breaks — then you inspect that area.

Boost Circuit

The boost circuit is a critical component that raises the 15V power supply input to approximately 18.5V. This boosted voltage powers the downstream chip groups. You can verify the boost circuit by measuring voltage across the boost output capacitor — it should read approximately 18.5V. If it reads significantly lower or zero, the boost circuit has failed and the downstream chips will not function. Common boost circuit failure causes include shorted output capacitors, failed boost controller IC, or damaged MOSFETs in the boost stage.

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. The BM1366BS chip on a 5nm process node is less forgiving of amateur repair attempts than the older, larger-geometry chips on S9 or S17 boards.

Fan Replacement

Fan replacement is the most common S19k Pro repair and the most approachable for DIY. Remember: the S19k Pro uses 4-pin square connector fans (120mm), shared with the T21 and S21 — not the 6-pin fans from the S19 Pro or S19j Pro.

Procedure:

1. Power off and unplug. Wait 5 minutes.
2. Remove the fan guard screws on the affected side (Phillips #2). There are typically 4 screws per fan guard.
3. Disconnect the fan power cable from the control board’s 4-pin header. Note the connector orientation — photograph first.
4. Remove the fan from the chassis. Note the airflow direction arrow on the fan housing.
5. Install the replacement fan with the airflow direction matching the original. Intake fans blow INTO the chassis; exhaust fans blow OUT. Getting this backwards will create a dead zone between the hashboards and dramatically increase chip temperatures.
6. Reconnect the fan power cable to the correct 4-pin header on the CVITEK C97 control board.
7. Secure the fan guard with the original screws.
8. Power on and verify the new fan appears in the dashboard with a healthy RPM reading between 4000–6000 RPM.

Power Supply Issues

The S19k Pro uses the APW12 power supply (12V–15V output). Despite the S19k Pro’s lower power draw (2760W vs 3250W for the S19 Pro), the APW12 is still working hard. Power delivery problems manifest as no startup, missing hashboards, low hashrate, random shutdowns, or elevated hardware error rates.

APW12 diagnostics:

• No LED on PSU: Check wall outlet voltage (200–240V AC required — 120V will not power an S19k Pro). 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 between PSU and miner chassis. A loose connection can deliver enough voltage to light LEDs but not enough current to run hashboards.
• Miner starts but hashboards intermittent: Under load, the APW12 must deliver stable current to all four hashboards. A failing PSU may sag under load — voltage drops below threshold and hashboards drop out. Measure voltage at the miner’s power input while all four boards are running.
• Voltage out of range: If the APW12 output drifts outside the 12–15V range, the miner may produce errors or fail to initialize hashboards. An aging PSU can develop capacitor drift that causes output voltage instability. Replacement is the solution.
• PSU fan not spinning: The APW12 has its own cooling fan. If it stops, the PSU will overheat and either shut down or produce unstable output. Check the PSU fan independently.

Hashboard Repair

Hashboard repair on the S19k Pro requires careful attention due to the BM1366BS chip’s 5nm geometry and tight component spacing. The 82-chip chain per board is shorter than the S19j Pro’s 126-chip chain, which makes individual chip identification somewhat easier, but the smaller chip package and finer-pitch solder balls demand more precision during physical repair work.

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 (12–15V DC) to the hashboard. Measure resistance between the power input pins to detect short circuits on the board itself.
2. Check voltage domain output — each domain should show approximately 0.34V. If the PSU shows correct voltage at the input but no domain voltage is present, the problem is in the power distribution circuitry on the board — check voltage regulators and their supporting components.
3. Check the EEPROM and PIC circuits — verify that the board identification and calibration data can be read. Measure 3.3V output at the appropriate test point. If there is no 3.3V, check the test fixture cable connection and consider reprogramming.
4. Check the boost circuit — measure voltage at the boost output. Should be approximately 18.5V. If significantly lower or zero, the boost circuit has failed.
5. Check LDO 1.2V and PLL 0.8V outputs — probe each LDO and PLL output pin. 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.

Scenario 2: Incomplete Chip Detection (Fewer than 82 chips found)

When the hashboard detects some but not all 82 chips, the problem is typically a single failed chip breaking the signal chain:

• ASICNG (X): If the display shows “ASICNG” followed by a number, 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. Inspect for cold solder joints on the chip itself. Among the chips in that domain group, look for abnormal pin soldering.
• Partial count (e.g., 70 out of 82): The board finds most chips at low baud rate but misses some at high baud rate. Use the binary search method to isolate the faulty chip:
  1. Short-circuit the RO test point and 1V2 test point at the midpoint of the chain (around chip 41).
  2. Run the detection test. If 41 chips are found, the first half is good.
  3. Move the short-circuit probe to the midpoint of the second half.
  4. Continue halving until the specific faulty chip is identified.
  5. Inspect the chip visually. If appearance is normal, replace it anyway — BM1366BS chips can be internally damaged with no visible external signs.

Scenario 3: Pattern NG (Nonce Response Data Incomplete)

When the test 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 group.
• If a cluster of chips shows low response rates, replace the chip with the lowest response rate in that group first.
• If the chip appearance is not visibly damaged, this typically indicates internal silicon degradation — the transistors within the 5nm chip have failed partially. Replacement is the only fix.

Scenario 4: All Chips Detected But Hashrate Low on One Board

When all 82 chips are detected but a specific hashboard is producing significantly less than its expected ~30 TH/s:

• Check hardware error (HW) count in the miner log for that chain. High HW errors indicate chips are working but producing bad nonces.
• Inspect chip temperatures — a hot spot on one area of the board causes the affected chips to throttle or produce errors.
• Check voltage stability across the hashboard’s power domains. A sagging domain voltage causes all chips in that domain to underperform.
• If HW errors are concentrated around specific chip positions, those chips may need re-flow or replacement.

BM1366BS Chip Replacement Procedure

For those with the required skills and equipment, here is the BM1366BS replacement procedure:

1. Pre-tin the replacement chip — apply solder paste (138°C low-temp) to the new BM1366BS chip pads before placing it on the board. The finer pitch of the BM1366BS requires more precision than older chips — use a magnifying lens or microscope.
2. Remove the faulty chip — use the hot air rework station to heat the chip evenly until the solder melts. Lift straight up with vacuum tweezers. Do not twist, rock, or pry the chip.
3. Clean the pads — use desoldering wick, flux, and circuit board cleaner to clean the PCB pads. Inspect under magnification for lifted, bridged, or damaged pads. Any pad damage must be assessed before proceeding.
4. Place and solder the new chip — align the pre-tinned BM1366BS chip on the cleaned pads using alignment marks on the PCB. Apply heat evenly with the rework station. Allow the solder to flow naturally — do not apply pressure.
5. Post-soldering inspection — check that the PCB has no visible deformation. Verify the replacement chip and all surrounding passive components are intact. Look for solder bridges between adjacent pads.
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 (room temperature) 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.

Control Board Issues

The S19k Pro uses the CVITEK CV1835 (Ctrl_C97) control board — a different platform from the Xilinx-based boards used in the S19 Pro and S19j Pro. The C97 runs different firmware and has different network and diagnostic characteristics. It manages communication with all four hashboards, controls fan speeds, connects to the mining pool, and runs the miner’s operating system.

Common control board problems:

• IP not detected on network: Check the Ethernet cable (try a different cable and port). Verify your 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 C97 board itself may be faulty. The CVITEK board can sometimes be recovered with a factory reset via the hardware reset button.
• Missing chain (fewer than 4 hashboards): If one of the four hashboard chains disappears from the dashboard, first check the physical ribbon cable connection. 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 — 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 of the C97 processor itself. 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 to the correct 4-pin headers. Check the control board headers for bent or broken pins. The C97 board reads fan speed via the tachometer wire in the 4-pin connector — a damaged tach wire will report no fan even if the fan is spinning.

Temperature Sensor Troubleshooting

The S19k Pro uses multiple temperature sensors on each hashboard to monitor chip and PCB temperatures. These sensors are typically located on the back of the PCB, with their matching resistors on both the front and back surfaces. Accurate temperature readings are critical because the firmware uses them to control fan speed, trigger thermal throttling, and initiate emergency shutdowns.

When the test fixture reports sensor NG or abnormal temperature readings:

1. Inspect the temperature sensor ICs for proper soldering — cold joints on sensor chips are a common cause of erratic readings.
2. Check the pull-up and pull-down resistors associated with each sensor circuit. Measure their values and compare against the expected specification.
3. Verify the 3.3V power supply rail to the temperature sensor circuit is present and stable.
4. Check the physical contact between the sensor chip and the heatsink — poor thermal contact causes the sensor to report temperatures that do not reflect actual chip temperatures.
5. Inspect the heatsink for deformation — a warped heatsink causes uneven chip cooling, creating real temperature differences that the sensors correctly report as abnormal. The fix in this case is heatsink replacement, not sensor repair.
6. If a sensor consistently reads much higher or lower than its neighbors despite identical thermal conditions, the sensor IC itself may be damaged and need replacement.

Firmware & Software

Firmware Updates

Bitmain periodically releases firmware updates for the S19k Pro that can fix bugs, improve stability, and sometimes increase efficiency or hashrate. 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, skim a percentage of your block rewards, or install a backdoor. Verify firmware checksums before installing.
• Back up your configuration before updating — pool settings, network configuration, and any custom tuning profiles. Screenshot or export everything.
• Never interrupt a firmware update — if you see a green fast-blinking LED, the miner is actively writing firmware to flash. Power loss during this process can brick the CVITEK C97 control board, requiring a UART recovery procedure or board replacement.
• Test after updating — verify all four hashboards are detected, chip counts are at 82 each, and hashrate returns to normal (~120 TH/s) within 10 minutes of reboot.

Alternative Firmware Options

The S19k Pro is compatible with several third-party firmware options that offer features beyond Bitmain’s stock firmware. This is where the mining hacker really takes control:

• BraiinsOS+ — Open-source firmware with autotuning that optimizes each chip individually for maximum efficiency. Supports both underclocking (lower power, quieter, ideal for home mining and space heating) and overclocking (maximum hashrate for those with adequate cooling and power). BraiinsOS+ with autotuning can find the optimal operating point for each of the 328 BM1366BS chips individually, often achieving better J/TH efficiency than stock firmware. This is the go-to for home miners.
• LuxOS — Another third-party firmware option with advanced tuning features and fleet management capabilities for operators running multiple units.
• Vnish — Popular aftermarket firmware with aggressive tuning profiles for maximizing hashrate on well-cooled units.

Configuration Best Practices

• Change default credentials immediately — the default root / root is an open invitation. Set a strong, unique password. Anyone on your local network can access the miner’s web interface with default credentials.
• 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 backup. This prevents hashrate downtime that costs you money.
• Set appropriate fan speed profiles — if your firmware supports it, configure fan speeds that balance noise and cooling for your environment. For home mining with underclocked hashrate, running fans at 50–65% speed is often sufficient and much quieter than 100%.
• Enable monitoring — configure email or webhook alerts for hashrate drops, temperature warnings, or hashboard disconnections. Catching problems early saves money and prevents cascading failures.
• Document your settings — screenshot or export your pool configuration, network settings, and tuning profiles. If you need to re-flash firmware or replace the control board, having your settings documented saves time and reduces downtime.
• Keep the firmware current — but do not update blindly. Read release notes and community feedback before applying firmware updates. Some updates fix real bugs; others introduce new ones. Give a new firmware version a week in the community before deploying it to your production machines.

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 on the S19k Pro:

Maintenance & Repair Decision Flowchart

When a hashboard fails, follow this systematic approach to avoid wasted time and unnecessary component replacements. Discipline in diagnosis saves money in repair:

1. Routine Inspection
   • Visually inspect the board for PCB deformation, scorching, burnt marks, misaligned components, or missing passives.
   • Test the impedance of each voltage domain to detect short circuits or open circuits before applying power.
   • Each domain voltage should be approximately 0.34V.
2. Chip Test (PT1)
   • Use the hashboard test fixture to identify how many of the 82 chips are detected.
   • The test fixture log will report the chip count and any specific error codes.
   • 82/82 chips detected: proceed to PT2 functional test.
   • Fewer than 82: proceed to fault location.
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. Follow the signal direction to find the break point.
   • Use the binary search (dichotomy) method for partial detection failures.
4. Repair
   • Try re-flow first: add flux around the suspect chip, heat to allow solder to re-wet. This fixes cold solder joints without chip replacement.
   • If re-flow does not fix the issue, replace the BM1366BS chip following the procedure above.
   • Inspect and replace any damaged passive components (resistors, capacitors) identified during diagnosis.
5. Verify
   • After repair, let the board cool completely to room temperature.
   • Test at least twice on the test fixture. Both tests must pass.
   • For chip replacement repairs: cooling is especially important before testing — a hot board produces false NG results.
   • After reinstallation in the miner, monitor the repaired board for 24 hours to confirm stability.

Home Mining Optimization

The S19k Pro is one of the best S19-generation miners for home deployment, thanks to its superior efficiency. Here are specific optimization strategies that D-Central’s customers have successfully deployed:

Noise Reduction

• Underclock with aftermarket firmware: Running at 1200–1800W instead of 2760W drops fan speed dramatically. Most home miners report the S19k Pro becomes “barely noticeable” at 1500W in a basement or garage setting.
• Replace stock fans with quieter alternatives: The stock fans prioritize airflow volume over noise. Aftermarket fans with the same 4-pin square connector but optimized for lower noise can reduce dB levels while maintaining adequate cooling at underclocked power levels.
• Use duct shrouds: A 6-inch or 8-inch duct shroud on the exhaust side directs hot air into ductwork, reducing noise propagation and allowing you to route the heat where you want it.
• Isolation mounting: Place the miner on vibration-damping pads to reduce structural noise transmission through floors and shelving.

Heat Recovery — The Space Heater Strategy

At 2760W (stock) or 1200–1800W (underclocked), the S19k Pro produces between 4,000 and 9,400 BTU/h of heat. That is equivalent to a medium-to-large portable electric space heater — except this one earns Bitcoin while it runs. Canadian winters make this strategy especially compelling.

• Use an exhaust shroud to duct warm air into the room you want to heat.
• At underclocked settings, the S19k Pro can heat a medium-sized room (200–400 sq ft) comfortably.
• Monitor with a smart thermostat — some advanced firmware options support temperature-based hashrate control, but a simple smart plug with temperature monitoring works too.
• In summer, either shut down, reduce power further, or duct the exhaust outside through a window.
• D-Central’s Bitcoin Space Heater line provides purpose-built enclosures for this exact use case.

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 at home and what requires professional intervention. The S19k Pro’s 5nm BM1366BS chips demand more precision than older-generation chips during board-level repair. Here is an honest assessment:

DIY-appropriate tasks:

• All routine maintenance (cleaning, visual inspection, thermal gel replacement)
• Fan replacement (use correct 4-pin square connector fans)
• Ribbon cable troubleshooting and replacement
• Firmware updates and configuration
• PSU swaps
• Control board replacement (C97 to C97)
• Basic diagnostics via dashboard and SSH
• Noise reduction modifications (shrouds, underclocking, fan swaps)

Professional repair required:

• BM1366BS chip replacement (BGA rework with fine-pitch 5nm chip)
• EEPROM reprogramming or replacement
• Boost circuit repair (controller IC, MOSFETs, output capacitors)
• Damaged PCB traces or pad repair
• Multiple chip failures on a single board
• Voltage regulator failures
• Temperature sensor IC replacement
• Any repair requiring an oscilloscope for signal tracing
• Control board UART recovery after bricked firmware

The S19k Pro’s 82 chips per board and 5nm process node make professional repair especially valuable. A board-level technician with the right equipment can diagnose and fix a specific chip failure efficiently. An amateur attempting the same repair without experience can turn a $60 fix into a destroyed $400+ hashboard. The BM1366BS’s finer solder ball pitch is significantly less forgiving than the BM1398 or BM1362 during rework. Know your limits, and know when to call in the experts.

Interactive Hashboard Schematic

Explore the ANTMINER S19K 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.