Buy now the A20B-1008-0740 — Atlantechdrives provides this FANUC E-Stop Unit Printed Circuit Board, the dedicated emergency stop control board for FANUC R-J3iC and R-30iA robot controllers. A critical safety-circuit component for FANUC robot maintenance — available with worldwide express delivery and 12-month warranty.
What Is the A20B-1008-0740?
The A20B-1008-0740 is the Emergency Stop (E-Stop) Unit PCB installed inside FANUC R-J3iC and R-30iA robot controllers. It is the dedicated hardware circuit responsible for processing and routing all emergency stop signals within the robot controller safety chain — including signals from the teach pendant E-stop button, the operator panel E-stop, the fence interlock gate contacts, and any external peripheral emergency stop devices connected to the controller’s safety I/O. When any E-stop signal is activated, the A20B-1008-0740 board immediately removes the servo-ready signal from the servo amplifier, causing controlled de-energisation of all six robot axes. The board works in conjunction with the A20B-1008-0730 PLC Control Board, which is its companion board within the R-30iA controller architecture — together they handle the complete safety logic and machine I/O functions of the controller. The A20B-1008-0740 is a Japan-manufactured FANUC component, part of the A20B-1008 series of robot controller PCBs. As the R-30iA controller is one of FANUC’s most widely deployed robot controllers globally — used in automotive welding, assembly, material handling, and palletising applications — the demand for this replacement board remains consistently high in the industrial maintenance market.
Key Technical Specifications
- Part Number: A20B-1008-0740
- Board Type: E-Stop Unit PCB (Emergency Stop Control Board)
- Compatible Controllers: FANUC R-J3iC, FANUC R-30iA
- Function: Emergency stop signal processing and safety relay control
- Input Voltage: 24 VDC (from controller internal power supply)
- Companion Board: A20B-1008-0730 (PLC Control Board)
- PCB Series: A20B-1008 (FANUC R-30iA controller board family)
- Country of Origin: Japan
- Manufacturer: FANUC Ltd., Oshino-mura, Yamanashi, Japan
- Status: Available as surplus/replacement part
E-Stop Safety Circuit Architecture in the R-30iA
The R-30iA controller implements a dual-channel safety architecture for emergency stop monitoring, compliant with ISO 10218-1 (Robot Safety) and IEC 62061 (Safety of Machinery). The A20B-1008-0740 E-Stop PCB monitors multiple independent E-stop input channels simultaneously: the teach pendant DEADMAN switch and E-stop button, the operator panel E-stop button, the EAS1/EAS2 fence interlock inputs (used for safety gate monitoring), the SVOFF external servo-off input, and any daisy-chained external E-stop devices connected to the controller’s TBOP/TBSF terminal block. The board processes these inputs through redundant relay logic — a failure in either channel triggers the E-stop response independently, ensuring single-fault safety. When the E-stop circuit is activated, the board removes the SRVO-001 servo ready condition, causing the FANUC amplifier to execute a Category 0 or Category 1 stop depending on the controller configuration and the nature of the E-stop source. Failure of the A20B-1008-0740 board typically manifests as persistent SRVO-001 (Servo Amp Not Ready) or SRVO-003 (Deadman switch released) alarms that cannot be cleared even with the E-stop button released and the teach pendant enable switch in the correct state.
Maintenance Tips
Before replacing the A20B-1008-0740, always verify that the E-stop alarm is not caused by a wiring fault in the external safety circuit — particularly in the EAS1/EAS2 fence interlock inputs. Disconnect the external devices from the TBOP terminal block one at a time and attempt to clear the E-stop alarm after each disconnection to isolate whether the fault is in the PCB or in an external safety device. A common source of false E-stop activation in R-30iA installations is contamination or mechanical wear in the teach pendant DEADMAN switch — check the teach pendant cable and switch before condemning the E-stop board. When replacing the A20B-1008-0740, power down the R-30iA controller completely and wait for all capacitors to discharge before opening the controller cabinet — do not attempt a live board swap on the E-stop unit as this constitutes a safety violation. After installing the replacement board and powering up, verify correct E-stop operation by deliberately activating each E-stop source individually (teach pendant, operator panel, fence gate) and confirming that the robot stops correctly and the alarm clears when the E-stop is released.
Frequently Asked Questions
Q: What FANUC alarms typically indicate a failed A20B-1008-0740 E-Stop PCB?
A: The most common alarms associated with A20B-1008-0740 failure are SRVO-001 (Servo amplifier not ready — E-stop input active when it should not be), SRVO-003 (Deadman switch released), and SRVO-230 (E-stop board fault). If these alarms appear persistently with no apparent cause in the external safety circuit and cannot be cleared by releasing all E-stop buttons and enabling the teach pendant, the E-stop PCB itself should be suspected.
Q: Is the A20B-1008-0740 compatible with both the R-J3iC and R-30iA controllers?
A: Yes. The A20B-1008-0740 is confirmed compatible with both the FANUC R-J3iC and the R-30iA robot controllers. These controllers share the same board architecture for the E-stop and PLC functions. Always verify the controller model and board revision before ordering to ensure exact compatibility.
Q: Does replacing the A20B-1008-0740 require any software reconfiguration of the R-30iA?
A: No software reconfiguration is required. The E-stop unit board does not store robot parameters or program data — all configuration resides in the R-30iA controller’s main CPU memory. After installing the replacement board, the controller will resume normal E-stop monitoring automatically. However, a full E-stop functional test of all safety inputs must be performed before returning the robot to automatic production.
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