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| Place of Origin | JAPAN |
| Brand Name | FANUC |
| Certification | CE ROHS |
| Model Number | A20B-3900-0160 |
The FANUC A20B-3900-0160 is a 16MB FROM / 1MB SRAM memory module in the A20B-3900 family.
It is commonly listed for 16i, 18i, and 21i controls and is described as a small modular board that plugs into the main master PCB alongside CPU, graphics, FSSB, and other memory hardware.
That installation style makes the A20B-3900-0160 a very specific internal control-memory component rather than a general replacement PCB.
For service work, it is most useful when the CNC still has production value and the correct 16MB FROM / 1MB SRAM module is needed to keep the original controller structure intact.
| Parameter | Value |
|---|---|
| Part Number | A20B-3900-0160 |
| Brand | FANUC |
| Product Type | Memory Module / Memory Board |
| Module Type | FROM / SRAM Module |
| FROM Capacity | 16MB |
| SRAM Capacity | 1MB |
| Commonly Listed Controls | 16i / 18i / 21i |
| Mounting Style | Plug-in module on main master PCB |
| Typical Use | CNC control memory replacement |
The A20B-3900-0160 is best suited to memory replacement in 16i, 18i, and 21i controls, especially where the control still uses the original internal memory-board structure and requires a direct module replacement.
It is a strong fit for CNC repair stock, board-level controller restoration, and service support for older i-Series equipment.
It also makes sense in workshops that handle recurring FANUC control repairs, because the model is already associated with a known plug-in memory-board role on the main master PCB.
That makes it practical for technicians who want predictable fit and consistent board-level replacement procedures.
Q1: What is the actual role of A20B-3900-0160 inside the control?
The A20B-3900-0160 is a 16MB FROM / 1MB SRAM module used in the internal memory structure of FANUC controls, particularly 16i, 18i, and 21i systems.
Seller descriptions identify it as a small plug-in memory module that installs on the main master PCB, alongside other major boards such as CPU, graphics, and FSSB-related hardware.
That means it is not a peripheral option card, but part of the controller’s core internal memory arrangement.
Q2: What do the FROM and SRAM sections do in practical terms?
A hardware list for the relevant FANUC control family states that CNC control software programs are stored in the FROM and that the SRAM part is battery-backed.
In practical maintenance terms, that means the module is responsible for more than generic storage.
It supports both program retention and stored controller data behavior, which is why memory-board replacement should always be handled with more care than a simple plug-in card exchange.
Q3: Why is this module widely used in 16i, 18i, and 21i controls?
Because sellers consistently identify it with 16i, 18i, and 21i control families and describe it as a plug-in memory module for the i-Series main board.
That gives the part a well-defined field application: it is a memory component used where those control families still rely on the original board-level storage arrangement.
In real service work, that makes it a common replacement candidate in long-life i-Series maintenance.
Q4: What are the biggest risks when replacing A20B-3900-0160?
The main risks are incorrect module matching, connector damage, and loss of stored system data or settings if the replacement is done without preparation.
Since the module contains both FROM and battery-backed SRAM functions, technicians should confirm the exact installed model, protect available backups, and inspect the receiving socket on the master board before fitting the replacement.
With memory boards, the mechanical installation is usually the easy part; preserving the control’s original operating state is the more sensitive task.
Q5: Why should buyers choose the exact A20B-3900-0160 instead of another 16MB module?
Because the memory family includes several boards that may share a 16MB FROM figure but differ in SRAM size, intended control family, or installation role.
The A20B-3900-0160 is specifically identified as 16MB FROM / 1MB SRAM for i-Series master-board applications, and that exact combination is what makes it the correct part.
In industrial repair, matching only the headline memory size is not enough; the full module identity matters.
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