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| Place of Origin | JAPAN |
| Brand Name | FANUC |
| Certification | CE ROHS |
| Model Number | A20B-3900-0229 |
The FANUC A20B-3900-0229 is a 16MB FROM / 512KB SRAM module in the A20B-3900 family.
It is commonly listed as a memory board for 16i, 18i, and 21i Model B controls, and one seller describes it as a small plug-in module mounted onto the main board alongside other control boards and memory devices.
That placement makes it a very specific control-memory component rather than a general replacement PCB.
In service terms, the module is most useful where a FANUC control still relies on its original memory hardware and needs the exact 16MB FROM / 512KB SRAM configuration to preserve the intended board layout and retained data structure.
| Parameter | Value |
|---|---|
| Part Number | A20B-3900-0229 |
| Brand | FANUC |
| Product Type | FROM / SRAM Module |
| FROM Capacity | 16MB |
| SRAM Capacity | 512KB |
| Product Family | A20B-3900 series |
| Commonly Listed Controls | 16i / 18i / 21i Model B |
| Mounting Style | Plug-in memory module on main board |
The A20B-3900-0229 is best suited to memory replacement for 16i, 18i, and 21i Model B controls, particularly where the control remains serviceable and a direct board-level memory swap is the most efficient repair option.
It is also well suited to CNC memory repair inventory, legacy control support, and board exchange work where maintaining the original Model B memory structure matters more than using a loosely similar replacement.
It is especially practical in shops that regularly service Model B controls, because the module is already identified by sellers as a known fit for that control group.
That makes it a sensible spare for recurring repair needs in older i-Series installations.
Q1: What kind of module is A20B-3900-0229?
It is a 16MB FROM / 512KB SRAM memory module used in FANUC control-memory applications, particularly for 16i, 18i, and 21i Model B systems.
Q2: Where is this module installed?
Seller descriptions place it as a plug-in memory module on the main board, alongside other major control boards and memory cards.
That means it belongs inside the controller memory stack, not in the operator panel or drive amplifier.
Q3: Why is the 512KB SRAM value important?
Because SRAM capacity is one of the defining features of the module. Even if another A20B-3900 board appears similar, a different SRAM value can mean a different memory configuration and a different intended fit.
Q4: Is this mainly a repair-market part?
Yes. The way it is sold today is strongly oriented toward replacement, surplus, and service use, which makes it much more relevant to repair and restoration than to new machine development.
Q5: Why should buyers match the exact part number?
Because the A20B-3900 family includes several memory modules with different FROM and SRAM combinations.
Matching A20B-3900-0229 exactly is the safer way to maintain compatibility in a Model B control.
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