Fanuc PC Back Panel BI Circuit Board Components PCB A20B-2003-0150

FANUC A20B-2003-0150 | 2-Slot Backplane PCB — Series 16i / 18i / 21i Model B / Yellow Housing / Discontinued

The Backplane That Holds Model B Together

The A20B-2003-0150 is the 2-slot backplane PCB that lives inside the yellow housing unit (A02B-0236-D100) of FANUC's i-Series CNC controllers — specifically the Model B variants of the Series 16i, 18i, and 21i. The backplane is not a processing card. It is the electrical bus and mechanical mounting structure that allows the other cards in the rack to talk to each other and to the rest of the CNC system.

Its two expansion slots accept Sub-CPU option boards — additional function cards that extend the 16i/18i/21i Model B's capabilities beyond the base CPU configuration. Whatever option cards are installed in the rack, they all plug into and communicate through this backplane. If the backplane fails, none of the boards plugged into it are reachable from the main system, even if those boards are individually functional.

The small secondary PCB A15L-0001-0060#A — the connector board that routes signals to the cooling fans and to the backup battery — also attaches at a defined point on the A20B-2003-0150. This secondary board is a routine part of the backplane assembly rather than a separately stocked item.

Key Specifications

Model B — Not Interchangeable with Model A

The A20B-2003-0150 is exclusive to the Model B hardware generation of the 16i, 18i, and 21i families. Model A controllers use a different backplane design. The housings look similar from the outside; the backplane PCB inside determines the generation. Confirm the CNC is a Model B variant from its configuration label before ordering this backplane. A Model A controller with a failed backplane requires a different part number.

When the backplane is replaced, the option boards removed from the original backplane reinstall into the replacement. No reprogramming of the option boards is required by the backplane swap itself — the data they hold is stored on those boards, not on the backplane.

FAQ

Q1: What symptoms indicate the A20B-2003-0150 backplane has failed?

A failed backplane typically produces alarms related to all option boards simultaneously — the CNC cannot detect or communicate with any of the cards in the expansion slots. If removing and reseating all option boards and checking connector integrity does not restore communication, the backplane itself is the fault source. Single-board failures with other boards still visible to the CNC suggest an individual board fault rather than the backplane.

Q2: Is the A20B-2003-0150 compatible with Series 21i Model B as well as 16i and 18i Model B?

Yes. The yellow housing A02B-0236-D100 with the A20B-2003-0150 backplane is used across Series 16i, 18i, and 21i Model B CNC controllers. The physical backplane and housing are common across these models — the specific CNC system software and CPU configuration determine which series the complete controller is identified as.

Q3: The A15L-0001-0060#A fan-battery board is damaged. Is it included with A20B-2003-0150?

The A15L-0001-0060#A is a separate component that mounts on the backplane assembly. It is not automatically included when ordering the A20B-2003-0150 backplane PCB alone. If both the backplane and the fan-battery board are damaged, both must be sourced separately. Confirm which components are included when ordering from the aftermarket.

Q4: Must option boards be reprogrammed after the backplane is replaced?

No. The option boards (Sub-CPU boards) store their own data and configuration. Replacing the backplane PCB they plug into does not change the data on those boards. Simply remove the option boards from the failed backplane, confirm they are undamaged, and reinstall them in the replacement backplane. Verify all boards are recognised by the CNC at first power-on after replacement.

Q5: Where is the A20B-2003-0150 sourced after discontinuation?

Through the FANUC i-Series CNC aftermarket — FANUC parts dealers, CNC specialist repair services, and tested surplus suppliers. Confirm Model B specifically before ordering — the backplane for Model A controllers is a different part number. Specify A20B-2003-0150 from the installed board's label.