A20B-2901-066
May 22, 2026

A20B-2901-066

Model: A20B-2901-066 (often written as A20B-2901-0660) Type: CNC main PCB / PMC (Programmable Machine Control) module Manufacturer: FANUC Function: Core control board for FANUC Series 16/18 CNC systems; integrates CPU, system memory, PMC logic, I/O control, and communication ports. Executes CNC programs, manages servo/spindle axes, and handles machine I/O and panel communications. Weight: Approx 0.11–0.20 kg Status: Discontinued; available as new surplus, refurbished, or used

Description

Specifications

  • Processor: FANUC custom 32-bit RISC CPU

  • Memory: Typically 4 MB DRAM, 2 MB flash (system/PMC)

  • Power Supply: DC 24V (auxiliary), DC 5V (on-board logic)

  • I/O: 24 digital inputs / 16 digital outputs (24VDC); 2 analog inputs (0–10V)

  • Communication: 2×RS-232, 1×RS-422/485, parallel I/F, FANUC bus interface

  • Operating Temp: 0°C to +40°C (non-condensing)

  • Storage Temp: -20°C to +60°C

  • Humidity: 5%–95% RH (non-condensing)

  • Protection: Overvoltage, overcurrent, ESD, surge, and short-circuit protection

Compatibility

  • CNC Systems: FANUC Series 16i, 18i, 21i (legacy 16/18)

  • Servo/Spindle: αi/βi series amplifiers (A06B-6110/6130)

  • Machine I/O: FANUC I/O units, operator panels, and peripheral devices

Safety Instructions

  1. Power off and wait ≥5 minutes for capacitor discharge before servicing.

  2. Use an anti-static wrist strap to prevent ESD damage to sensitive components.

  3. No hot-plugging of cables or connectors; power down first.

  4. Do not modify on-board circuits or jumpers; this will void warranty and risk damage.

Installation

  1. Shut down main power and lockout/tagout the system.

  2. Insert the board into the designated CNC slot and secure with screws.

  3. Connect 24V DC power, communication cables (RS-232/422), I/O wiring, and FANUC bus.

  4. Verify all connectors are fully seated and locked.

  5. Restore power; check LED status and perform a cold start with PMC/CNC program reload.

Maintenance

  1. Clean dust from the PCB surface and connectors quarterly.

  2. Inspect connectors for looseness, corrosion, or bent pins.

  3. Check on-board LED indicators for fault codes during operation.

  4. Keep the control cabinet dry, free of oil mist, and within temperature specs.

Troubleshooting

  1. No power/LEDs off: Check 24V DC supply and board seating.

  2. PMC alarm: Reload PMC program; check I/O wiring and ground connections.

  3. Communication failure: Verify RS-232/422 cables, baud rate, and handshake settings.

  4. CNC boot failure: Check flash memory and reload CNC system software。


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