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| Place of Origin | JAPAN |
| Brand Name | FANUC |
| Certification | CE ROHS |
| Model Number | A20B-3900-0163 |
The FANUC A20B-3900-0163 is listed as a 32MB FROM / 1MB SRAM module. It is associated with 16i, 18i, and 21i Model A controls and is described as a small plug-in memory board that fits onto the main master PCB alongside the CPU, graphics, FSSB, and other memory-related boards.
That makes it a specific control-memory part for i-Series architectures rather than a general spare PCB.
This kind of module matters because it sits directly in the storage path for controller-side software and retained data.
It is also a board that should be handled with backup discipline: one service listing notes that data will be lost during replacement and needs to be restored, which is exactly the kind of point maintenance teams need to know before starting a swap.
For a product page, the best description is straightforward: A20B-3900-0163 is a FANUC i-Series memory module used where the control requires the correct 32MB FROM + 1MB SRAM hardware to keep the original memory structure intact.
That makes it a natural fit for board replacement, spares holding, and controller restoration on installed 16i/18i/21i systems.
| Parameter | Value |
|---|---|
| Part Number | A20B-3900-0163 |
| Brand | FANUC |
| Product Type | FROM / SRAM Module |
| FROM Capacity | 32MB |
| SRAM Capacity | 1MB |
| Applicable Controls | 16i / 18i / 21i Model A |
| Mounting Style | Plug-in module on main master PCB |
| Typical Use | Control memory replacement |
The A20B-3900-0163 is well suited to 16i / 18i / 21i control maintenance, especially where the system uses a 32MB FROM + 1MB SRAM plug-in memory module on the main system board.
It is commonly used in machines with more complex control configurations, larger ladders, and memory layouts that depend on the correct i-Series plug-in module rather than a generic replacement card.
It also fits controller memory upgrade support, repair of failed FROM/SRAM modules, and long-term spare-parts planning for installed i-Series equipment.
For service departments, this module is most valuable when the original control is still worth keeping in operation and memory hardware needs to be restored without changing the rest of the CNC platform.
Q1: What is A20B-3900-0163 used for?
It is a 32MB FROM / 1MB SRAM memory module for 16i/18i/21i Model A controls. It plugs into the controller’s main board area and supports the control-memory structure used by that hardware family.
Q2: Is this the same as A20B-3900-0160?
No. They are different modules. A20B-3900-0160 is listed as 16MB FROM + 1MB SRAM, while A20B-3900-0163 is listed as 32MB FROM + 1MB SRAM. They should not be treated as the same part.
Q3: What should be done before replacement?
Back up the control data first. One service listing states that data will be lost during replacement and must be restored afterward, so a board swap should be planned as both a hardware and a data task.
Q4: Where is this module installed?
It is described as a small modular device that plugs into the main master PCB alongside other major control boards and memory devices. That means it belongs to the controller’s internal memory stack, not to the operator panel or drive amplifier.
Q5: When is this module most useful?
It is most useful when a 16i/18i/21i control still has value in service and needs the correct memory hardware to restore the original controller configuration. That is why it fits repair shops, maintenance inventory, and replacement work for installed i-Series machines.
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