WhatsMiner M50S++ Error 202 / 250: Communication & Chip Count Repair
ASICREPAIR.in Technical Team
TL;DR
MicroBT Error 202 indicates 0 hashboard detection, while Error 250 signals incomplete chip count (e.g. 102/105 chips active). Both stem from broken KF1968 signal lines or corrupted EEPROM data.
WhatsMiner M50S++ Error 202 / 250: Communication & Chip Count Repair
⚠️ Quick Summary: On MicroBT WhatsMiner M50S++ rigs, Error 202 indicates total loss of hashboard communication (0 boards found), whereas Error 250 means the control board detected fewer than the required 105 KF1968 ASIC chips on a board.
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📊 Error Code Breakdown & Diagnostic Differences
| Error Code | Console Status Message | Root Failure Cause | Primary Hardware Target | | :--- | :--- | :--- | :--- | | Error 202 | `Hashboard count mismatch (found 0/3)` | 14.5V PSU DC output missing or control cable broken | P221C PSU / 14-pin data cable | | Error 250 | `Chip count incomplete (found 98/105)` | Broken CLK / RI signal line at chip #98 | KF1968 Chip #98 or LDO regulator | | Error 350 | `Control board voltage out of range` | Blown input protection diode on control board | CB IO board voltage divider |
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🔬 Electrical Test Point Measurements (KF1968 Chips)
Test the following reference points on the M50S++ hashboard PCB:
``` Main DC Input Bar: 14.5V DC (Supplied by P221C power supply) Domain Voltage: 0.38V DC per domain across 28 series domains LDO Communication VDD: 1.80V DC (Powering signal transceiver ICs) Signal Line CLK: 50MHz clock frequency (0.9V DC measured with multimeter) Signal Line RI: 1.80V DC active state (Drops to 0.0V on reset) ```
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🛠️ Step-by-Step Troubleshooting for Error 250
Step 1: Identifying the Faulty Chip Index
1. Connect via SSH to the WhatsMiner IP address or read the system log in WhatsMinerTool. 2. Locate the line: `SM 0 bad chip id: 98`. This tells you Chip #98 is failing to return the Read-Out (RO) signal.Step 2: Measuring Signals at Chip #98
1. Power up the board on the test fixture. 2. Place the black multimeter probe on PCB Ground (GND) and red probe on Pin 4 (RI) of Chip #97: - If Chip #97 RI = 1.8V but Chip #98 RI = 0.0V, the trace between Chip #97 and Chip #98 is broken, or Chip #98 input pin is shorted.Step 3: Desoldering & Replacing the KF1968 ASIC Chip
1. Apply Kester 951 flux over KF1968 Chip #98. 2. Preheat the bottom of the PCB to 150°C using a preheating plate to prevent board warping. 3. Heat top die with Atten ST-862D at 380°C for 30 seconds until solder melts. 4. Replace with an original KF1968 ASIC chip, align BGA dots, and reflow.---
💡 Humidity & Dust Protection in Indian Mining Operations
🌧️ Monsoon Season Corrosion Alert:
In humid regions like Mumbai, Chennai, or Kolkata, high relative humidity (above 85%) causes copper dendrite growth between adjacent 1.8V and GND pads under KF1968 chips. We recommend ultrasonic washing of hashboards with specialized solvent followed by conformal coating application.
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❓ Frequently Asked Questions
Can I mix KF1921 chips with KF1968 chips on an M50S++ board?
No. KF1921 and KF1968 chips have different internal silicon step architectures and core voltage requirements. Mixing them will cause instant Error 250 locks.Why does my P221C PSU click off 5 seconds after turning on?
When the control board detects Error 202 or 250, it sends a shutdown signal to the P221C PSU to prevent thermal runaway. This clicking is a protective trip, not necessarily a broken PSU.---
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