1 PC Used Fanuc A20B-2100-0390 PCB Board In Good Condition A20B21000390 A2OB-21OO-O39O

A20B-2100-0390 | FANUC FSSB Basic I/O Module PCB — A02B-0236-C211 / IOU1 / FANUC i CNC / Power Mate i / αi PS HV

A02B-0236-C211 — The FSSB I/O Module (IOU1)

The A20B-2100-0390 is the printed circuit board inside the FANUC A02B-0236-C211 FSSB Input/Output Module. This module — designated IOU1 (I/O Unit 1) — provides distributed I/O connectivity for FANUC i-series CNC controls and Power Mate i controllers.

In FANUC's i-series CNC architecture, FSSB-connected I/O modules extend the CNC's machine I/O capacity by placing I/O nodes close to the actual machine devices — sensors, solenoids, limit switches, and panel buttons. The IOU1 communicates with the CNC via the FSSB (Fibre-optic Servo Serial Bus) rather than through traditional parallel I/O wiring, using high-speed serial data transfer over optical fibre.

Key Specifications

24V DC Input — FUSE 1 Diagnostic Note

The A02B-0236-C211 FSSB I/O module's 24V DC power input is protected by FUSE 1 on the A20B-2100-0390 PCB. A practical diagnostic indicator:

LED1 status check: The module has an LED1 that illuminates when the 24V supply is healthy. If LED1 does not light after power-up, the first diagnostic step is to check FUSE 1 for continuity using a multimeter. A blown fuse is replaced after identifying and resolving its cause — a downstream short circuit or overload condition in the module's connected I/O wiring.

This onboard fuse protection is a standard safety feature — preventing damage to the A20B-2100-0390 PCB from overcurrent events in the machine's 24V I/O wiring.

Application Scenarios

FSSB I/O module fault — LED1 not lit: A FANUC i-series CNC machining centre loses communication with an FSSB I/O node. The module's LED1 is dark. FUSE 1 on A20B-2100-0390 is found blown. After correcting the 24V wiring fault, the fuse is replaced and I/O communication is restored.

αi PS HV power supply control board replacement: A FANUC αi PS HV power supply module (A06B-6150 series) develops control-level faults. The A20B-2100-0390 control PCB is identified. Replacement restores power supply module operation.

FAQ

Q1: What is FSSB, and how does the IOU1 module use it?

FSSB (Fibre-optic Servo Serial Bus) is FANUC's high-speed serial bus for connecting the CNC to servo drives and I/O modules. The A02B-0236-C211 IOU1 module with A20B-2100-0390 connects to the CNC via the FSSB fibre-optic cables — receiving I/O commands from the CNC and returning I/O status data over the same serial link. This replaces traditional parallel I/O wiring with a single fibre pair, enabling distributed I/O nodes anywhere along the FSSB chain.

Q2: What CNC systems are compatible with the A02B-0236-C211 IOU1 module (with A20B-2100-0390)?

The IOU1 module is confirmed for FANUC i CNC Controls and Power Mate i (Models D and H). The Power Mate i series is FANUC's compact CNC controller integrated with servo drive systems — typically used in single-axis or limited-axis automated equipment. The FANUC i series refers to the i-generation CNC platform (Series 0i, 16i, 18i, 21i) that uses FSSB for servo and I/O communication.

Q3: Why is the same A20B-2100-0390 PCB found in both the FSSB I/O module and the αi PS HV power supply?

FANUC's modular design philosophy reuses verified PCB designs across different hardware platforms where the underlying electronic functions — signal processing, microcontroller execution, communication interfaces — share sufficient commonality. The A20B-2100-0390 PCB design satisfies the control and communication requirements of both the FSSB I/O module and the αi PS HV power supply housing, with the specific application determined by the PCB's software and external connector configuration within each module.

Q4: After replacing A20B-2100-0390 in the IOU1 module, does the CNC I/O configuration need to be changed?

No. The I/O address assignments and configuration for the FSSB I/O module are stored in the CNC's parameter memory — not in the module's PCB. After fitting the replacement A20B-2100-0390 and verifying the 24V power supply and FSSE fibre connections, the CNC should re-establish communication with the module using the existing I/O configuration. Verify all I/O points function correctly through the PMC diagnosis screen before returning to production.

Q5: What safety precautions apply when accessing A20B-2100-0390 inside the module?

Handle with a grounded anti-static wrist strap on an ESD-safe surface. For the IOU1 module: switch off the machine's 24V control supply before accessing the module. For αi PS HV power supply applications: switch off and lock out mains power, then verify the DC bus has fully discharged before accessing internal components — the HV power supply operates at high DC bus voltages that persist after mains removal.