1771-A4B | Allen-Bradley PLC-5 16-Slot Universal I/O Chassis
1771-A4B | Allen-Bradley PLC-5 16-Slot Universal I/O Chassis
1771-A4B | Allen-Bradley PLC-5 16-Slot Universal I/O Chassis
    1771-A4B | Allen-Bradley PLC-5 16-Slot Universal I/O Chassis
1771-A4B | Allen-Bradley PLC-5 16-Slot Universal I/O Chassis

1771-A4B | Allen-Bradley PLC-5 16-Slot Universal I/O Chassis

Part #: 1771-A4B Manufactured by: Allen-Bradley
$1,145.00
$1,145.00
3 in Stock
Condition: New – Open box
Shipping calculated at checkout.
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 16-slot universal I/O chassis designed for PLC-5 systems. It provides the backplane power and communication structure for 1771-series input/output modules and supports industrial-grade installations requiring robust, scalable I/O architecture. Designed for back-panel mounting, this chassis delivers up to 24 A backplane current at 5VDC and is engineered for durability in demanding plant environments.

 

 

Technical Specifications 

Condition New / Never Used Surplus
Brand Allen-Bradley
Manufacturer Rockwell Automation
Series PLC-5 / 1771 I/O
Part Number 1771-A4B
Product Type I/O Chassis
Total Slots 16
Backplane Current (5VDC) 24 A
Mounting Type Back Panel
Enclosure Type Open Style
Operating Temperature 0–60°C (32–140°F)
Storage Temperature -40–85°C
Relative Humidity 5–95% non-condensing
Operating Shock 15 g
Non-Operating Shock 30 g
Vibration 2 g @ 10–500 Hz
Dimensions 12.4 x 24 x 7.6 in (chassis body)
Location Type Stand-Alone or System Integrated
Module Compatibility 1771 PLC-5 I/O Modules

  

 

Information About 1771-A4B

The Allen-Bradley 1771-A4B is a versatile PLC-5 universal I/O chassis offering sixteen (16) module slots for a wide range of 1771 I/O and specialty modules. It contains the full backplane circuitry necessary for powering and interconnecting installed modules and provides hinged field wiring arms for convenient installation and maintenance. This chassis is designed to work in industrial environments with an operating temperature range of 0–60°C (32–140°F) and humidity tolerance of 5–95% non-condensing. Shock and vibration ratings of 15 g (operating shock) and 2 g at 10–500 Hz (vibration) ensure long-term reliability.

Key Features:

  • Universal I/O chassis for Allen-Bradley PLC-5 systems
  • Sixteen (16) module slots for flexible system design
  • Backplane supports up to 24 A at 5V DC
  • Designed for back-panel mounting
  • Compatible with all 1771 I/O and specialty modules
  • Rugged design with high shock and vibration tolerance
  • Open-style enclosure for cabinet integration
  • Hinged field wiring arms for fast module replacement
  • Ideal for standalone or expandable PLC-5 systems
  • A durable, high-capacity I/O chassis providing the structural and electrical backbone for Allen-Bradley 1771 and PLC-5 automation systems

This chassis is part of the 1771 Classic I/O family, known for modularity, high flexibility, and broad application compatibility. Modules can be replaced without rewiring thanks to removable wiring arms. The 1771-A4B supports both standalone and system-integrated installations with strong expansion capability through the PLC-5 platform.

 

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.

IQElectro is not an authorized distributor.
IQElectro LLC (IQElectro) is NOT an Authorized Distributor or in any way affiliated with Rockwell Automation, Siemens, or any other Manufacturers. IQElectro is NOT an Authorized Dealer of this product. The product may be of older version, date codes, or design than that available from authorized dealers. As IQElectro is not an authorized dealer of this product, the Original Manufacturer's Warranty and Support DO NOT apply. IQElectro sells SURPLUS only and DOES NOT SELL SOFTWARE or FIRMWARE licenses For more detailed information, please refer to the full version of our disclaimer policy Disclaimer Policy.
Description / Specifications

Description

The Allen-Bradley 1771-A4B is a 16-slot universal I/O chassis designed for PLC-5 systems. It provides the backplane power and communication structure for 1771-series input/output modules and supports industrial-grade installations requiring robust, scalable I/O architecture. Designed for back-panel mounting, this chassis delivers up to 24 A backplane current at 5VDC and is engineered for durability in demanding plant environments.

 

 

Technical Specifications 

Condition New / Never Used Surplus
Brand Allen-Bradley
Manufacturer Rockwell Automation
Series PLC-5 / 1771 I/O
Part Number 1771-A4B
Product Type I/O Chassis
Total Slots 16
Backplane Current (5VDC) 24 A
Mounting Type Back Panel
Enclosure Type Open Style
Operating Temperature 0–60°C (32–140°F)
Storage Temperature -40–85°C
Relative Humidity 5–95% non-condensing
Operating Shock 15 g
Non-Operating Shock 30 g
Vibration 2 g @ 10–500 Hz
Dimensions 12.4 x 24 x 7.6 in (chassis body)
Location Type Stand-Alone or System Integrated
Module Compatibility 1771 PLC-5 I/O Modules

  

 

Information About 1771-A4B

The Allen-Bradley 1771-A4B is a versatile PLC-5 universal I/O chassis offering sixteen (16) module slots for a wide range of 1771 I/O and specialty modules. It contains the full backplane circuitry necessary for powering and interconnecting installed modules and provides hinged field wiring arms for convenient installation and maintenance. This chassis is designed to work in industrial environments with an operating temperature range of 0–60°C (32–140°F) and humidity tolerance of 5–95% non-condensing. Shock and vibration ratings of 15 g (operating shock) and 2 g at 10–500 Hz (vibration) ensure long-term reliability.

Key Features:

  • Universal I/O chassis for Allen-Bradley PLC-5 systems
  • Sixteen (16) module slots for flexible system design
  • Backplane supports up to 24 A at 5V DC
  • Designed for back-panel mounting
  • Compatible with all 1771 I/O and specialty modules
  • Rugged design with high shock and vibration tolerance
  • Open-style enclosure for cabinet integration
  • Hinged field wiring arms for fast module replacement
  • Ideal for standalone or expandable PLC-5 systems
  • A durable, high-capacity I/O chassis providing the structural and electrical backbone for Allen-Bradley 1771 and PLC-5 automation systems

This chassis is part of the 1771 Classic I/O family, known for modularity, high flexibility, and broad application compatibility. Modules can be replaced without rewiring thanks to removable wiring arms. The 1771-A4B supports both standalone and system-integrated installations with strong expansion capability through the PLC-5 platform.

 

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