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| Place of Origin | JAPAN |
| Brand Name | FANUC |
| Certification | CE ROHS |
| Model Number | A20B-3900-0225 |
The FANUC A20B-3900-0225 is a 32MB FROM / 3MB SRAM R301A module in the A20B-3900 series.
It is commonly used in FANUC i-Series controls such as 16i, 18i, and 21i, and it is installed as a FROM/SRAM module for the control-memory structure rather than as a display board or drive PCB.
This model stands out because of its 3MB SRAM capacity, which gives it a different profile from many other A20B-3900 modules.
In maintenance work, that makes exact part-number matching especially important.
It is a practical replacement part for systems where the original memory layout must be preserved to keep the control operating in its intended configuration.
Some listings also note that after replacement, FROM files, parameters, and programs must be reloaded, which is a meaningful service detail for technicians preparing a swap.
In real repair work, that means the module should be treated as both a hardware part and a data-sensitive service item.
| Item | Specification |
|---|---|
| Part Number | A20B-3900-0225 |
| Brand | FANUC |
| Product Type | FROM / SRAM Module |
| Module Type | R301A Module |
| FROM Capacity | 32MB |
| SRAM Capacity | 3MB |
| Control Family | FANUC i-Series |
| Typical Application | 16i / 18i / 21i controls |
The A20B-3900-0225 is well suited to memory replacement in 16i / 18i / 21i controls, especially where the machine still uses the original i-Series memory architecture and needs the correct FROM/SRAM module to stay in operation.
It is also a strong fit for controller restoration, board exchange stock, and service support for LCD-mounted i-Series hardware.
It is particularly useful in situations where a defective memory module must be replaced without changing the rest of the CNC platform.
In those cases, the correct 32MB/3MB configuration is more important than using a physically similar memory card from the same family.
Q1: What is A20B-3900-0225 used for?
It is a 32MB FROM / 3MB SRAM R301A memory module used in FANUC i-Series controls such as 16i, 18i, and 21i. Its role is in the controller memory structure, not in the drive or panel section.
Q2: Why is the 3MB SRAM capacity important?
Because SRAM size is part of the board’s identity and directly affects compatibility inside the control. A module with a different SRAM capacity may belong to the same family but still not be the correct replacement for this application.
Q3: Does anything need to be restored after replacement?
Yes. One listing specifically notes that FROM files, parameters, and programs must be reloaded after replacing this module, so replacement should be planned as both a hardware task and a data-restoration task.
Q4: Where is this module most useful?
It is most useful in i-Series CNC repair work, especially when a 16i, 18i, or 21i control still has production value and needs the exact memory module to return to service.
Q5: Why not replace it with any A20B-3900 memory card?
Because the A20B-3900 family includes multiple module sizes and memory combinations.
The safer approach is to match the exact A20B-3900-0225 model to preserve the intended memory structure.
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