FANUC A20B-3900-0240 CNC FROM/SRAM Memory Card

Description

Product Introduction

The FANUC A20B-3900-0240 is a specialized mainboard memory card designed for FANUC Series 30i, 31i, 32i, and 35i CNC control systems. Inserted directly into dedicated DIMM expansion slots on the main CPU PCB (such as A16B-3200 series motherboards), this board houses both Flash ROM (FROM) and static random-access memory (SRAM) needed for high-speed CNC boots and real-time execution.

Engineered for seamless integration with FANUC’s i-series hardware, the card holds system core software, PMC ladder files, and user macro programs. The onboard SRAM section retains part programs, pitch error compensation values, and coordinate systems when the main machine power is switched off.

Key Technical Specifications

Application Scenarios & The “Trench” Experience

During a cold morning startup on a multi-axis CNC turn-mill center, the control failed to boot past the Initializing screen, triggering a persistent system memory parity alarm. Diagnostics revealed that localized static discharge during a maintenance cycle had corrupted the onboard SRAM array on the original memory DIMM. Installing a verified A20B-3900-0240 card and restoring the system from a clean SRAM backup restored the CNC to full operation without replacing the expensive main CPU board.

• High-Axis Machining Centers & Lathes – Stores extended part programs, complex 5-axis surface contours, and high-capacity tool offset tables.
• Automated Transfer & Gantry Lines – Holds complex PMC ladder routines managing multi-station interlocks and auxiliary automation.
• System Upgrades & Board Swaps – Transfers complete machine configuration state quickly when replacing main motherboard hardware.

A20B-3900-0240

A20B-3900-0240

Transparency SOP: Quality Assurance & Testing

1. Edge-Connector Pin Inspection: Gold-plated DIMM contacts and surface-mount IC leads are inspected under high magnification for micro-cracks, contamination, or wear.
2. Read/Write Cycle Bench Test: Inserted into a dedicated FANUC 31i-B mainboard test stand to verify Flash ROM read integrity and SRAM write/erase cycles.
3. Power-Cycle Data Retention Sweep: The module undergoes simulated battery disconnect/reconnect tests to ensure zero data corruption occurs across the SRAM retention block.
4. ESD Safe Packaging: Verified cards are washed with precision electronics cleaner, sealed in anti-static shielding bags, and packaged in custom anti-static foam inserts.

The Veteran’s Tech Trap Guide

• ⚠️ BACKUP ALL DATA BEFORE REMOVING! Removing the A20B-3900-0240 module without a fresh SRAM backup (via Memory Card or USB in BOOT SYSTEM mode) will permanently wipe user programs, tool offsets, and machine parameters.
• ❗ Observe ESD grounding protocols. Memory DIMM modules are exceptionally sensitive to electrostatic discharge. Always wear a grounded anti-static wrist strap when handling the card or working inside the main CNC motherboard rack.
• ⚠️ Do not force the module during insertion. Align the physical notch on the gold contacts with the keyway inside the DIMM socket. Press evenly on both corners until the side locking clips click fully into place.

Frequently Asked Questions

• Q: Can I swap an A20B-3900-0240 from one machine to another?

  A: Physically yes, but the target machine will load the parameters, PMC ladder, and software options stored on that specific card. You must restore the target machine’s correct SRAM backup file after swapping.

• Q: How do I know if my memory card is failing?

  A: Common signs include system freeze during boot loader sequences, recurring SRAM Parity Alarms (SRAM PARITY ERROR), or sudden loss of part programs after turning off the main disconnect switch.

• Q: Are these original OEM FANUC components?

  A: Yes, 100%. We supply only authentic OEM FANUC circuit modules, fully bench-tested on genuine FANUC CNC control systems prior to dispatch.