1771-A4B | Allen-Bradley PLC-5 I/O Chassis Assembly, 16 Slot, Back-panel mount
1771-A4B | Allen-Bradley PLC-5 I/O Chassis Assembly, 16 Slot, Back-panel mount
1771-A4B | Allen-Bradley PLC-5 I/O Chassis Assembly, 16 Slot, Back-panel mount
    1771-A4B | Allen-Bradley PLC-5 I/O Chassis Assembly, 16 Slot, Back-panel mount
1771-A4B | Allen-Bradley PLC-5 I/O Chassis Assembly, 16 Slot, Back-panel mount

1771-A4B | Allen-Bradley PLC-5 I/O Chassis Assembly, 16 Slot, Back-panel mount

Part #: 1771-A4B Manufactured by: Allen-Bradley
Regular price
$1,152.00
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$1,152.00
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Condition: New-Surplus Original Box
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Product Overview
Allen Bradley PLC 5 I/O Chasis, 16 Slots, 24 Amperes, Back Panel Mount Type
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Product Description P/N: 1771-A4B

Description / Specifications

Description 

The Allen-Bradley 1771-A4B is a universal I/O chassis. This hardware is a Sixteen (16) slot chassis that is used to provide backplane connectivity and house 1771 PLC modules. It provides a maximum backplane Current of 24 A and designed for panel installation.

 

Technical Specifications 

Brand Allen-Bradley
Manufacturer Rockwell Automation
Part Number 1771-A4B
Dimensions 3.5 x 6.5 x 2.0 in (89 x 165 x 51 mm)
Vibration 2 g (at 10-500 Hertz)
Nonoperating Shock 30 g
Operating Shock 15 g
Enclosure Type Open Style
Mount Type Back Panel
Max Backplane Current (at 5 Volts DC) 24 Amperes
Number of Module I/O Slots 16 Slots
Module Type I/O Chasis
Location Stand-Alone
Relative Humidity 5-95% non-condensing

  

 

Information About 1771-A4B

The Allen-Bradley 1771-A4B is a universal I/O chassis that is part of the 1771 Programmable Logic Controller (PLC) product family. This chassis features Sixteen (16) I/O slots, which hosts the electronic circuitry, specifically the backplane, for distributing power to the attached modules. It also hosts the hinges for field wiring arms.

The 1771-A4B is designed to be operated at a temperature range of 32-140 Degree Fahrenheit or 0-60 Degree Celsius while the hardware’s storage temperature is -40 to 185 Degree Fahrenheit or -40 to 85 Degree Celsius. It has a relative humidity of 5-95% noncondensing. When installing this universal I/O chassis, maintain panel vibration and shock within 2g at 10-500 Hz and 15g, respectively.

The 1771-A4B is capable of receiving power via 1771 processor with integral power supplies that provided 2-4 Amperes, power supply modules with rated output of 3-8 Amperes and external power supplies with output Current of 6.5-16 Amperes. As a general rule, never install an external power supply and a power supply module to the 1771-A4B. This power supply connection is not compatible and will disqualify the hardware configuration.

The 1771-A4B chassis has 16 I/O slots. It has dimensions of 12.4 x 24 x 7.6 in. and weighs 14.8 lbs. For installation in a 1771 PLC-5 system, it uses the back-panel mounting method with adequate spacing and an open enclosure. The chassis backplane has a power supply of 8A at 5V DC.

The 1771-A4B chassis has a universal configuration for chassis mounting and system design because of its own consistent design. 1771 I/O modules are small, flexible, cost-effective, and provide a complete range of digital, analog, and intelligent I/O modules for various applications. I/O modules come with wiring arms and remote termination panels, eliminating the need for disconnecting the wire to replace the module. For troubleshooting and diagnostics, status indicators are present on the front of the modules. For future expansion, it can be easily replaced with a larger chassis. It is intended for use in an industrial environment with a 0 - 60 °. Celsius (32 - 140 deg. Fahrenheit) operating temperature, 5-95 % noncondensing relative humidity, and a 30g operating shock.



Manufacturer information

Allen-Bradley, a brand of Rockwell Automation, specializes in manufacturing industrial automation equipment. The product range includes programmable logic controllers (PLCs), motion control systems, safety devices, motor control equipment, automation software, and HMI panels. Allen-Bradley products are known for their reliability and integration with other systems.

Frequently Asked Questions about 1771-A4B
Question: What is the main function of the 1771-A4B?
Date Update:12/06/2025
Answer:

The Allen-Bradley 1771-A4B is a universal I/O chassis used to house and power up to 16 I/O modules in the PLC-5 control system. It acts as the physical and electrical backbone for connecting various input and output modules via a shared backplane. This chassis distributes both power and communication signals between the processor and modules. It allows for centralized or distributed control applications depending on the system layout. Its design supports flexible system expansion and modularity.

Question: What is the maximum backplane current of this chassis?
Date Update:12/06/2025
Answer:

The 1771-A4B is capable of supporting up to 24 Amperes at 5 Volts DC through its backplane. This current is shared among all the installed I/O modules. The backplane not only powers the modules but also carries control signals to and from the processor. It’s important to calculate the total load to avoid exceeding power limits. Overloading may result in voltage drops or damage to the system components.

Question: What power supply options are compatible with 1771-A4B?
Date Update:12/06/2025
Answer:

This chassis can be powered by a 1771 processor with built-in power supply (2–4 A), an external power supply module (3–8 A), or a dedicated external supply (6.5–16 A). However, it is not recommended to use both a power module and external supply simultaneously. Doing so could result in electrical conflicts or hardware damage. Power supply choice depends on the total current demand of the installed modules.

Question: Are status indicators available on the chassis?
Date Update:12/06/2025
Answer:

While the chassis itself does not include status LEDs, many 1771 I/O modules feature front-facing indicators. These lights provide quick diagnostics about input status, output state, or module health. They assist with troubleshooting and verification during system startup or failure events. The wiring arms also include labeling for ease of identification. Additional diagnostics are available via processor or SCADA interfaces.

Question: Is the 1771-A4B chassis still supported and available?
Date Update:12/06/2025
Answer:

Although the 1771 series has been largely superseded by newer platforms like ControlLogix and CompactLogix, the 1771-A4B remains available through select distributors and as spare parts. It is widely used in legacy PLC-5 systems and supported by Rockwell Automation. For new designs, Rockwell recommends migration to newer chassis systems. However, the 1771-A4B continues to serve reliably in many existing industrial applications.

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Description / Specifications

Description 

The Allen-Bradley 1771-A4B is a universal I/O chassis. This hardware is a Sixteen (16) slot chassis that is used to provide backplane connectivity and house 1771 PLC modules. It provides a maximum backplane Current of 24 A and designed for panel installation.

 

Technical Specifications 

Brand Allen-Bradley
Manufacturer Rockwell Automation
Part Number 1771-A4B
Dimensions 3.5 x 6.5 x 2.0 in (89 x 165 x 51 mm)
Vibration 2 g (at 10-500 Hertz)
Nonoperating Shock 30 g
Operating Shock 15 g
Enclosure Type Open Style
Mount Type Back Panel
Max Backplane Current (at 5 Volts DC) 24 Amperes
Number of Module I/O Slots 16 Slots
Module Type I/O Chasis
Location Stand-Alone
Relative Humidity 5-95% non-condensing

  

 

Information About 1771-A4B

The Allen-Bradley 1771-A4B is a universal I/O chassis that is part of the 1771 Programmable Logic Controller (PLC) product family. This chassis features Sixteen (16) I/O slots, which hosts the electronic circuitry, specifically the backplane, for distributing power to the attached modules. It also hosts the hinges for field wiring arms.

The 1771-A4B is designed to be operated at a temperature range of 32-140 Degree Fahrenheit or 0-60 Degree Celsius while the hardware’s storage temperature is -40 to 185 Degree Fahrenheit or -40 to 85 Degree Celsius. It has a relative humidity of 5-95% noncondensing. When installing this universal I/O chassis, maintain panel vibration and shock within 2g at 10-500 Hz and 15g, respectively.

The 1771-A4B is capable of receiving power via 1771 processor with integral power supplies that provided 2-4 Amperes, power supply modules with rated output of 3-8 Amperes and external power supplies with output Current of 6.5-16 Amperes. As a general rule, never install an external power supply and a power supply module to the 1771-A4B. This power supply connection is not compatible and will disqualify the hardware configuration.

The 1771-A4B chassis has 16 I/O slots. It has dimensions of 12.4 x 24 x 7.6 in. and weighs 14.8 lbs. For installation in a 1771 PLC-5 system, it uses the back-panel mounting method with adequate spacing and an open enclosure. The chassis backplane has a power supply of 8A at 5V DC.

The 1771-A4B chassis has a universal configuration for chassis mounting and system design because of its own consistent design. 1771 I/O modules are small, flexible, cost-effective, and provide a complete range of digital, analog, and intelligent I/O modules for various applications. I/O modules come with wiring arms and remote termination panels, eliminating the need for disconnecting the wire to replace the module. For troubleshooting and diagnostics, status indicators are present on the front of the modules. For future expansion, it can be easily replaced with a larger chassis. It is intended for use in an industrial environment with a 0 - 60 °. Celsius (32 - 140 deg. Fahrenheit) operating temperature, 5-95 % noncondensing relative humidity, and a 30g operating shock.



Manufacturer information

Allen-Bradley, a brand of Rockwell Automation, specializes in manufacturing industrial automation equipment. The product range includes programmable logic controllers (PLCs), motion control systems, safety devices, motor control equipment, automation software, and HMI panels. Allen-Bradley products are known for their reliability and integration with other systems.

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