The FANUC A20B-8100-0135 is an LCD-mounted motherboard and main control PCB for FANUC Series 18i-A CNC systems without the personal-computer function. It supports the CPU, axis control, display control, memory modules and external CNC interfaces.

FANUC documentation identifies A20B-8100-0135 as the Series 18i motherboard with hardware ID C5. It is installed behind the LCD section of compatible 18i-A controls, but the CNC model, PCB revision and installed cards must be confirmed before replacement.

A20B-8100-0135 Product Information

Main Board Functions and Interfaces

A20B-8100-0135 connects the controller's processor, memory and control cards. Documented interfaces include FSSB, MDI, two RS-232C ports, I/O Link, serial spindle or position coder, F-BUS and video. Available functions still depend on the installed cards, software and machine configuration.

Compatibility and Revision Checks

Match the complete A20B-8100-0135 number, slash revision, 18i-A control model, CPU card, axis card, display card, memory modules and boot software. Later revisions use ECC checking for SRAM data, so mixing hardware and boot-software generations without restoring a valid backup can cause a parity or ECC alarm.

Testing and Replacement Notes

REACO CNC checks the label, connectors, power rails, CPU and memory recognition, boot process, display output and available communication functions under an applicable test configuration. Back up SRAM data before removal and restore the correct software, parameters, programs and machine data after installation. Qualified personnel should isolate power and use ESD protection.

Related resources: FANUC PCB boards, FANUC CNC controls and FANUC CNC repair services.