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| Place of Origin | JAPAN |
| Brand Name | FANUC |
| Certification | CE ROHS |
| Model Number | A20B-2000-0670 |
The FANUC A20B-2000-0670 belongs to one of the most enduring PCB families in FANUC's product history — the A20B-2000 series.
This series covers the CNC control hardware for a substantial and diverse range of FANUC controller generations that collectively represent tens of thousands of machine tools installed in factories worldwide. The installed base of machines using A20B-2000 series hardware remains meaningful even decades after FANUC discontinued these boards, because the machine tools themselves continue to operate productively and require maintenance support.
The A20B-2000 family takes its breadth from the diverse role these boards played in FANUC's controller architecture of the era.
At the structural end: backplane boards that provide the rack interconnection for plug-in modules, spanning from compact 2-slot backplanes for small controller configurations to 6-slot backplanes for the most fully-optioned systems.
At the functional end: master CPU boards like the A20B-2000-0170 (the famous Zero-C master board that served the Series 0MC, 0TC, 0MD, and 0TD) and the A20B-2000-0180 (the expanded-bus version for more complex configurations), which were the backbone of arguably the most widely installed CNC controllers in the industry during the 1990s.
The A20B-2000-0670 occupies a position within this family as a CNC control board for FANUC industrial automation systems — serving the specific controller generation and configuration for which it was designed, as a board that maintenance engineers rely on to keep long-service FANUC-controlled machines running.
| Parameter | Value |
|---|---|
| Series | A20B-2000 |
| Type | CNC control PCB |
| Origin | Japan |
| Status | Discontinued — spare available |
| Application | FANUC industrial CNC systems |
What makes the A20B-2000 family worth understanding in depth is the longevity of the machines it served. FANUC CNC-controlled machine tools from the 1990s were built to last — the mechanical quality of lathes, machining centres, and grinding machines from this era was high, and the production economics of many manufacturing operations make continued operation of these machines preferable to replacement.
A 20-year-old CNC lathe that still holds its tolerances and has been well-maintained mechanically needs only reliable electronic spare parts to continue serving another decade of production.
This reality drives a genuine secondary market for A20B-2000 series boards. Specialist FANUC parts suppliers carry stock of overhauled, tested boards in this series because the demand from maintenance engineers worldwide justifies it.
When a production machine comes down due to an A20B-2000 series board failure, the cost of the repair (board replacement plus parameter reload labour) is a small fraction of the daily production output that stoppage represents — making a quick turnaround repair or exchange the only economically rational response.
The A20B-2000-0670 fits into this landscape as a board for which the above logic applies: it serves a specific role in a specific FANUC system generation, it has been discontinued by the manufacturer, and it continues to be needed by facilities maintaining equipment from that generation.
One of the distinguishing characteristics of FANUC as a manufacturer is the longevity of its installed base and the depth of the specialist service ecosystem that has developed around maintaining it.
Unlike some CNC control manufacturers where third-party parts support is thin, FANUC's dominant market position through the 1990s and 2000s created sufficient installed base to support a robust specialist repair and refurbishment industry.
For maintenance engineers working with A20B-2000 series equipment, the practical implications are:
Board availability: A20B-2000 series boards can be sourced in refurbished, tested condition from specialist FANUC parts suppliers.
These are not generic reproductions — they are original FANUC boards that have been overhauled, recapped, cleaned, and tested against known-good FANUC systems to verify functionality.
The quality of available refurbished boards varies by supplier, and selecting a supplier with FANUC-specific test equipment and a meaningful warranty (6–12 months minimum) is the appropriate standard.
Documentation: FANUC's maintenance manuals for the relevant CNC generation remain available, and the knowledge base of FANUC-trained technicians is broad. Diagnosing a board fault in an A20B-2000 series system follows established procedures that experienced FANUC engineers know well.
Parameter management: The most critical aspect of maintaining any FANUC CNC system is ensuring that machine parameters are backed up before they are needed.
For A20B-2000 series systems where the SRAM battery is aging (these batteries are now 25–35 years old in original installations), parameter backup is an immediate priority.
A system whose parameters have been lost requires reconstruction from the machine builder's documentation — a project that can take days and produces results that need extensive verification.
A20B-2000 series boards are legacy items — they are no longer in production, the supply of refurbished units is finite, and each board that fails beyond repair permanently reduces the total available pool for the installed base that needs them.
This reality makes proper handling and storage more important than it might be for currently-produced parts.
Storage: boards should be kept in original antistatic bags or appropriate ESD-safe packaging, in a temperature-controlled environment (10–30°C), away from moisture, direct sunlight, and any sources of static charge.
Boards stored in cardboard boxes on open shelves in a machine shop environment deteriorate faster than those properly stored.
Handling: always use ESD precautions — wrist strap, ESD mat, avoid contact with component surfaces.
For boards with battery-backed SRAM (which many A20B-2000 series boards contain), verify the backup battery voltage before installation — if the battery has depleted during storage, the SRAM data (if any was preserved) is already lost, and the board needs parameter loading before use.
Q1: How is the correct A20B-2000-0670 confirmed for a specific FANUC CNC system?
The most reliable confirmation method is to match the part number on the installed board's label with the replacement.
FANUC labels on PCBs include the A20B part number, the revision suffix (e.g., /02A, /03B), and in some cases a machine builder's internal reference.
Cross-reference this against the machine's electrical documentation or the FANUC hardware manual for the specific CNC generation.
Part numbers in the A20B-2000 family that differ by only the last two or three digits are often very different boards — confirm the full part number precisely.
Q2: The machine has not had its CNC parameters backed up in years. Can parameters be recovered if the board fails and SRAM data is lost?
If the SRAM battery has depleted and data is lost, parameters cannot be recovered from the board — they are gone.
The recovery path is: first, locate the machine builder's acceptance documentation, which should include the original parameter sheets; second, check whether the machine tool builder maintains a service department that can provide a parameter file for the specific machine serial number; third, manually re-enter parameters and recertify machine accuracy with test cuts. This process can take one to several days depending on the machine's complexity.
The clear lesson is to implement a scheduled parameter backup procedure immediately — monthly or after any maintenance that touches the CNC.
Q3: What are the signs that an A20B-2000 series board is failing before it fails completely?
Early warning signs of board degradation include: intermittent system alarms that clear on power cycle (especially memory-type alarms that suggest SRAM instability as the backup battery weakens); programs or parameters that change unexpectedly between power cycles (data corruption from a failing battery); erratic axis behaviour that cannot be traced to a mechanical or motor fault; and the SRAM low-battery alarm itself if the CNC software generates one.
Any of these symptoms should trigger an immediate parameter backup and a priority investigation of the board's battery and power supply status.
Q4: Can an A20B-2000 series board be sent to a repair centre even if the failure is complete?
Yes. FANUC repair centres that specialise in A20B-2000 series hardware typically perform component-level board diagnosis, replacing failed ICs, electrolytic capacitors, power regulators, and other failed components.
A board that has completely failed due to a localised fault (a blown voltage regulator, a shorted capacitor) is often repairable.
A board with extensive PCB damage from carbonisation or cracked substrate may not be repairable at economically reasonable cost.
The repair centre should perform a free or low-cost evaluation before committing to a repair price — this evaluation identifies the fault and determines whether repair is feasible.
Q5: Is the A20B-2000-0670 compatible with the FANUC Series 0 family of CNC controllers?
The A20B-2000 series was FANUC's primary board family for the Series 0 (and related Series 15/16 early generation) CNC controllers through the late 1980s and 1990s.
Different variants within the family serve different specific system configurations within these generations.
Compatibility of the A20B-2000-0670 with a specific controller model and generation should be confirmed against the machine's hardware documentation — part number matching against the original installed board is the definitive confirmation method.
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