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| Place of Origin | JAPAN |
| Brand Name | FANUC |
| Certification | CE ROHS |
| Model Number | A20B-8100-0136 |
The FANUC A20B-8100-0136 is a 21i-A LCD mounted main PCB with PMC-SA5, intended for control assemblies where the operator interface and the main board structure are closely integrated.
Public product listings and manual snippets align on that identification, and FANUC documentation for the 21i Model A family also describes the PMC-SA5 platform as the faster PMC option compared with PMC-SA1, with a basic instruction speed of 0.085 μs/step and a maximum ladder size of 16,000 steps.
In real maintenance work, that combination matters.
A board like this is not simply a display-side spare and not just a generic motherboard.
It belongs to an integrated LCD-mounted control format, so technicians usually replace it when they need to preserve the original 21i-A hardware arrangement and restore the intended PMC and main-board behavior without changing the surrounding control design.
| Item | Specification |
|---|---|
| Part Number | A20B-8100-0136 |
| Brand | FANUC |
| Product Type | Main PCB |
| Mounting Format | LCD mounted |
| Applicable Series | 21i-A |
| PMC Type | PMC-SA5 |
| Basic Instruction Speed | 0.085 μs/step |
| Max Ladder Capacity | 16,000 steps |
| Typical Use | Repair, replacement, maintenance support |
Where the original 21i-A control remains mechanically and electrically serviceable, replacing the exact LCD mounted main PCB is usually a cleaner solution than attempting a retrofit.
It keeps the existing control format intact, reduces engineering uncertainty, and fits the way industrial maintenance departments typically manage long-life CNC equipment.
Q1: What makes the A20B-8100-0136 different from a standard support PCB?
This model is identified as a 21i-A LCD mounted main PCB with PMC-SA5, so it combines main-board responsibility with an integrated control format rather than serving as a narrow-function add-on card.
In field service, that means it plays a more central role in system operation and is chosen for exact replacement rather than general substitution.
Q2: Why is PMC-SA5 important in this board description?
PMC-SA5 is a defined PMC system within the FANUC family, and the published specification shows it as the higher-speed option compared with PMC-SA1 in the same family context. That matters because ladder performance and available logic capacity affect how the machine handles PLC-side control tasks, interlocks, and peripheral coordination.
Q3: What symptoms might lead a technician to inspect this board?
Typical triggers include startup faults, unstable control behavior, LCD-mounted unit issues, persistent control-side alarms, or problems that remain after simpler causes such as cabling and power condition have already been checked. Because this is a main-board class part, symptoms may appear broader than a single display fault.
Q4: Should this board be treated as a direct fit part or a configurable repair item?
It should be treated as a model-specific replacement part. A board in this category is normally selected by exact part number and intended control family, because fit, internal role, and associated PMC type all matter.
In CNC service, direct part-number accuracy is a more reliable guide than appearance alone.
Q5: Why do buyers prefer the original board model instead of adapting a different control board?
Because the original model preserves the intended FANUC architecture. Adapting a different board can introduce unknowns in wiring, system behavior, or commissioning.
For production users, maintaining the original control path is usually safer, faster, and more predictable than a partial redesign.
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