Allen-Bradley 1756-A4 Standard Chassis | ControlLogix 4-Slot Rack — Replacement, Equivalent & Selection Guide
The Allen-Bradley 1756-A4 is a 4-slot standard chassis designed for the ControlLogix platform by Rockwell Automation. It serves as the physical backbone of a ControlLogix system, housing up to 4 I/O, communication, or controller modules. This page provides full technical specifications, compatible replacement models, application guidance, and a structured selection guide to help engineers and procurement teams make the right sourcing decision.
Technical Specifications
- Part Number: 1756-A4
- Platform: ControlLogix
- Number of Slots: 4
- Chassis Type: Standard (non-redundant)
- Backplane Communication: ControlLogix backplane bus
- Power Supply Compatibility: 1756-PA72, 1756-PB72, 1756-PA75, 1756-PB75 (sold separately)
- Operating Temperature: 0 °C to 60 °C (32 °F to 140 °F)
- Storage Temperature: -40 °C to 85 °C
- Relative Humidity: 5% to 95% (non-condensing)
- Dimensions (H × W × D): Approx. 146 mm × 185 mm × 144 mm
- Weight: Approx. 750 g (chassis only, without modules)
- Mounting: DIN rail or panel mount
- Agency Certifications: UL, CE, CSA
- Country of Origin: USA
Compatible Replacement & Equivalent Models
The following models are commonly evaluated as replacements or equivalents for the 1756-A4. Always verify slot count, power supply compatibility, and firmware requirements before substitution.
- 1756-A7 — 7-slot ControlLogix chassis; direct upgrade path when additional module capacity is needed
- 1756-A10 — 10-slot ControlLogix chassis; suitable for larger system expansions
- 1756-A13 — 13-slot chassis; high-density applications
- 1756-A17 — 17-slot chassis; maximum slot count in the standard ControlLogix family
- 1756-A4K — Conformal-coated variant of the 1756-A4 for harsh environments
- 1756-A4LXT — Extended-temperature variant (-25 °C to 70 °C) for extreme conditions
- 1756-A4SXT — SIL-rated safety chassis equivalent for functional safety applications
Note: All replacements must use a compatible 1756-series power supply and ControlLogix-compatible modules. Cross-platform substitution (e.g., CompactLogix 5069 chassis) requires full system re-engineering.
Why Choose the Original 1756-A4 Model
- Proven reliability in mission-critical manufacturing and process control environments worldwide
- Full Rockwell Automation ecosystem support — seamless integration with Studio 5000, RSLogix 5000, and FactoryTalk software
- Compact 4-slot footprint ideal for space-constrained control panels or distributed I/O architectures
- Long product lifecycle with Rockwell’s sustained support and spare parts availability
- Backward and forward compatibility with the broad ControlLogix module library (1756-series)
- Genuine OEM quality — sourced from authorized channels, ensuring warranty validity and firmware compatibility
Typical Applications
- Automotive assembly line control systems
- Oil & gas pipeline monitoring and SCADA integration
- Food & beverage processing with hygienic control requirements
- Water/wastewater treatment plant automation
- Pharmaceutical batch process control (21 CFR Part 11 environments)
- Distributed control architectures with remote I/O via EtherNet/IP or ControlNet
- Machine safety systems (when paired with GuardLogix controller)
System Compatibility
- Controllers: 1756-L6x, 1756-L7x, 1756-L8x ControlLogix series
- Communication Modules: 1756-EN2T (EtherNet/IP), 1756-CN2 (ControlNet), 1756-DNB (DeviceNet), 1756-DHRIO (DH+/RIO)
- I/O Modules: Full 1756-series digital and analog I/O
- Power Supplies: 1756-PA72 (120/240 VAC), 1756-PB72 (18–32 VDC), 1756-PA75, 1756-PB75
- Programming Software: Studio 5000 Logix Designer v21 and above; RSLogix 5000 v16+
- Not compatible with: CompactLogix (5069/5370), MicroLogix, SLC 500, or PLC-5 platforms without gateway/bridge modules
Selection Guide
Use the following criteria to determine whether the 1756-A4 is the right chassis for your application:
- Module count ≤ 4: 1756-A4 is the optimal compact choice
- Module count 5–7: Consider upgrading to 1756-A7
- Module count 8–10: 1756-A10 recommended
- Harsh/corrosive environment: Select 1756-A4K (conformal coat)
- Extreme temperature range: Select 1756-A4LXT
- Functional safety (SIL 2/3): Select 1756-A4SXT with GuardLogix controller
- Redundancy required: Use two 1756-A4 chassis with 1756-RM2/A redundancy module pair
- Budget-constrained retrofit: Certified refurbished 1756-A4 units available — contact us for pricing
Quality Assurance & Sourcing
- All units sourced from authorized distributors or verified secondary market channels
- Pre-shipment inspection: visual check, label verification, and functional backplane test where applicable
- Anti-counterfeit measures: holographic labels, serial number traceability, and OEM packaging verification
- Refurbished units (where offered) undergo full cleaning, inspection, and burn-in testing
- Packaging: ESD-safe anti-static bags, foam-lined cartons, and moisture barrier protection
- Lead time: In-stock items ship within 1–3 business days; special orders 5–15 business days
How to Order
- Confirm your required slot count and environment rating (standard / conformal / extended temp)
- Verify power supply compatibility (AC or DC input)
- Add 1756-A4 to cart, or contact us for volume pricing and lead time confirmation
- For urgent requirements, email support@konmask.com with your PO or RFQ
- International orders: provide HS code 8537.10 for customs clearance assistance
Replacement & Compatibility FAQ
Q: Can I replace a 1756-A4 with a 1756-A7 without changing my modules?
A: Yes. All 1756-series modules are slot-position independent. Simply move your existing modules into the new chassis and update the I/O configuration in Studio 5000 if slot assignments change.
Q: Is the 1756-A4 compatible with the newer 1756-L8x controllers?
A: Yes. The 1756-A4 chassis is compatible with all current ControlLogix controllers including the 1756-L81E, 1756-L82E, 1756-L83E, 1756-L84E, 1756-L85E, and 1756-L86E.
Q: Can I use a third-party power supply with the 1756-A4?
A: Rockwell Automation does not officially support third-party power supplies. Use of non-OEM power supplies may void warranty and cause compatibility issues.
Q: What is the difference between 1756-A4 and 1756-A4K?
A: The 1756-A4K features a conformal coating on the PCB for protection against moisture, dust, and corrosive gases. It is recommended for harsh industrial environments.
Q: Is a used/refurbished 1756-A4 reliable?
A: Certified refurbished units that have passed functional testing are a cost-effective option for non-critical or backup systems. We provide test reports upon request.
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