Antminer S19 Pro Hashboard Repair Guide

Step 1: Visual Inspection

Remove the hashboard from the miner and inspect under bright, angled light:

• Burnt or discolored components — especially around buck converters (every 2-chip domain has its own regulator)
• Cracked solder joints — the QFN package of the BM1398 is prone to cracked joints from thermal cycling
• Oxidized or corroded areas — especially the 18-pin connector and exposed copper areas
• Swollen capacitors — small ceramic caps near each domain's regulator
• Physical board damage — cracks, chips in the PCB, or delamination
• PIC chip area — look for damage near the PIC16F1704 (small 14-pin chip near the edge connector)
• EEPROM chip — verify the AT24C02D (8-pin SOIC) is intact

Step 2: Voltage Domain Testing (38 Domains)

The S19 Pro has 38 voltage domains — significantly more than the S21's 12. Each domain powers exactly 2 BM1398 chips with a target voltage of 0.36V.

2a: Domain Resistance Check (Power Off)

1. Set multimeter to resistance mode (Ω)
2. For each domain, measure between the positive output pad and ground
3. Expected: 5–15Ω (only 2 chips per domain)
4. Near 0Ω = shorted chip or capacitor
5. Open (OL) = broken connection

2b: Powered Voltage Measurement

Apply 12V power and measure each of the 38 domains:

Step 3: Signal Chain Testing

The 76 BM1398 chips are connected in a daisy chain for communication:

1. CLK verification: Check clock signal continuity from the connector through the chain
2. CI/RI chain test: Probe at the midpoint (chip #38) to determine which half has the break
3. Binary search: Continue halving until the break point is identified

Common S19 Pro chain issues:

• Failed chip #0 or chip #75 (first/last in chain) — causes "chain find 0 ASIC"
• Cold solder joint on a QFN chip — causes intermittent chip drops
• Corroded trace near board edge — moisture ingress from hashboard slot

Step 4: PIC Chip Diagnostics

The PIC16F1704 is a critical component unique to the S19 Pro (and other S19 series). It handles:

• Hashboard identification and serial number storage
• I2C bridge to temperature sensors (LM75A at 0x48–0x4B)
• Voltage monitoring
• Communication with the control board during initialization

PIC Failure Symptoms:

• "EEPROM read error" in kernel log
• Board detected but no temperature readings
• Board intermittently disappears from the miner
• "PIC communication error"

PIC Diagnostics:

1. Check the I2C bus with a multimeter:
   • SDA and SCL lines should read ~3.3V (pulled up) when idle
   • If either reads 0V, the I2C bus is shorted (possibly a failed PIC or sensor)
2. Check PIC supply voltage: 3.3V at the VDD pin
3. If the PIC is responsive but reports errors, it may need reprogramming

PIC Reprogramming:

1. Connect a PICkit 3 or PICkit 4 programmer to the PIC's ICSP pads on the hashboard
2. Use MPLAB IPE to erase and reprogram the PIC with the correct hex file
3. The hex file is specific to the S19 Pro hardware revision — using the wrong file will cause malfunction

Step 5: Component-Level Diagnosis

After identifying the problem area through voltage and signal testing:

Individual BM1398 chip testing:

1. Multimeter in diode mode
2. Probe between VDD pad and GND
3. Healthy: forward voltage drop 0.3–0.6V
4. Shorted: 0V or very low reading
5. Open: OL reading (may indicate lifted chip)

Buck converter testing: Each of the 38 domains has a dedicated buck converter circuit:

1. Check input (12V) at the converter
2. Check output (should be 0.36V when powered)
3. Test the inductor continuity
4. Check for shorted output capacitors

Temperature sensor testing: The LM75A sensors at 0x48–0x4B are accessed through the PIC I2C bridge:

1. If temp readings are -1 or 999, the sensor or I2C path has failed
2. Check the I2C pull-up resistors (4.7kΩ to 3.3V)
3. A failed sensor may need direct replacement (SOT-23-5 package)

Step 6: BM1398 Chip Replacement (QFN Rework)

The BM1398 uses a QFN (Quad Flat No-Lead) package, which is simpler to rework than BGA:

Removal:

1. Apply flux around all four sides of the chip
2. Preheat the board to 150°C
3. Apply hot air at 350°C with medium flow
4. The chip will release in 45–60 seconds
5. Lift the chip straight up with tweezers

Pad preparation:

1. Apply flux to the exposed pads
2. Use solder wick at 350°C to level any excess solder
3. Clean with IPA
4. The pads should have a thin, flat solder coating

Installation:

1. Apply a thin layer of solder paste to the pads (or tin the pads with a thin solder layer)
2. Apply flux to the new BM1398 chip's bottom
3. Align the chip carefully — the orientation dot must match the PCB marking
4. Apply hot air at 350°C until the solder reflows (~45 seconds)
5. The chip should self-align if pad tinning is even

QFN tip: Unlike BGA, QFN chips have exposed pads on the bottom AND a large ground/thermal pad in the center. Ensure the center pad has adequate solder for both thermal and electrical connection.

Step 7: Verification and Testing

1. Resistance check — verify the repaired domain reads 5–15Ω
2. Powered voltage test — all 38 domains at 0.34–0.38V
3. Full mining test:
   • Install hashboard in miner
   • Boot and check web dashboard
   • All 76 chips detected
   • Hashrate ~37 TH/s per board
   • Temperature readings normal
4. 24-hour burn-in — monitor for stability

# SSH verification
ssh root@<miner-ip>
cat /tmp/freq.txt    # All 76 chips should show frequency
cat /tmp/temp.txt    # Temperature readings from LM75A sensors
dmesg | grep chain   # Chain detection status