1756-A13 13-Slot Chassis Replacement Guide

Overview

The Allen-Bradley 1756-A13 is a rugged, 13-slot passive backplane chassis designed for the ControlLogix control platform. Serving as the physical and electrical skeleton of the PAC (Programmable Automation Controller) system, the chassis distributes low-voltage DC power to installed modules and enables high-speed data transmission via its integrated backplane bus.

Over decades of service in demanding industrial environments, standard chassis units are subjected to continuous thermal cycling, vibrations, airborne contaminants, and corrosive agents. Standard wear-and-tear often manifests as degraded socket contacts, backplane traces damaged by localized overcurrent events, or physical damage to alignment guides.

Whether you are performing emergency maintenance on a failed unit or executing a planned system modernization, this guide details the engineering parameters, compatible replacements, and step-by-step physical replacement mechanics required to safely swap your 1756-A13 chassis without data loss or prolonged downtime.

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Legacy Product Information

The 1756-A13 chassis has gone through multiple series variations (Series A, B, and C). While early Series A and B units are considered legacy or discontinued, the Series C variation remains active but is often sourced as a direct replacement part. The chassis is a purely passive biological component of the physical assembly—it contains no processor, firmware, or active integrated ICs, acting entirely as a bus routing board with standardized DIN connectors.

Absolute Maximum Backplane Current Ratings

• 1.2V DC Bus: 1.5 Amperes
• 3.3V DC Bus: 4.0 Amperes
• 5.1V DC Bus: 15.0 Amperes
• 24V DC Bus: 2.8 Amperes

Operating Specifications & Physical Properties

• Power Dissipation: 4.5 Watts (maximum heat load generated by backplane traces under peak distribution)
• Isolation Voltage: 1350V AC continuous (between backplane and chassis frame for surge isolation)
• Dimensions (WxHxD): 508 x 145 x 137 mm (20.0 x 5.7 x 5.4 inches)
• Operating Temperature Range: 0°C to +60°C (32°F to +140°F) for standard units
• Vibration Resistance: 2.0 g operational acceleration at 10 to 500 Hz (conforming to IEC 60068-2-6)
• Cabinet Compatibility: Direct panel mounting (open-style) or standard 19-inch rack frames via optional mounting brackets

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Recommended Replacements

When replacing a 1756-A13, you have several options depending on physical enclosure constraints, environmental factors, and the availability of newer hardware revisions.

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Compatibility Considerations

Power Supply Mechanical Compatibility

The 1756-A13 accepts several standard ControlLogix power supply units that mount directly to the left-hand side of the chassis frame. Compatible power supplies include:

• AC Power Supplies: 1756-PA72 (Series B only), 1756-PA75 (Series A & B)
• DC Power Supplies: 1756-PB72 (Series B only), 1756-PB75 (Series A & B)
• Redundant Power Systems: 1756-PS13 power supplies connected via the 1756-CPR2 cable to a 1756-PAR2 or 1756-PBR2 scanner module mounted on the chassis.

Caution: When transferring an older 1756-PA72 or 1756-PB72 power supply to a new Series C chassis, confirm the chassis mounting tabs are aligned. Some legacy Series A power supply brackets require specific mounting screws or adapters to lock firmly into the alignment chassis of Series C variations.

Backplane Speed & Module Generations

While legacy standard modules (such as the 1756-L61/L63 ControlLogix 5560 controllers or early 1756-ENBT modules) run seamlessly on all 1756-A13 series, modern ControlLogix 5580 controllers (1756-L81E, L82E, etc.) and high-speed communications adapters (1756-EN4TR) require a Series C chassis to take advantage of the upgraded Gigabit Ethernet backplane bus communication speeds. Utilizing a Series A or B legacy chassis with 5580 series processors limits internal data structures.

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Upgrade Benefits

Upgrading an older 1756-A13 chassis to the newest Series C revision provides several distinct operational advantages:

• Upgraded Bus Architecture: Series C features enhanced internal signal isolation and physical trace improvements designed to guarantee high-frequency communications integrity, drastically dropping packet retries on high-density EtherNet/IP networks.
• Upgraded Grounding Strip Design: The structural grounding plane of the Series C utilizes revised spring-tension contact points, ensuring lower overall impedance to the chassis DIN rail ground. This vastly improves the electromagnetic compatibility (EMC) of the entire module rack.
• Greater Thermal Resiliency: Optimized materials used in the backplane structure maintain rigid alignments and resist warp deformation during heavy cyclic thermal changes common in high-density cabinets.

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Common Migration Challenges

• Chassis Grounding Issues: Often, system integrators fail to verify the continuity of the chassis frame grounding screw to the back-panel mounting plate. Without a direct low-impedance path, electrostatic dissipation can occur through the active modules, causing hardware faults.
• Physical Footprint Variations: While the mounting-hole centers of the 1756-A13 Series A, B, and C are identical, the depth dimensions can vary marginally when specific older power supplies are mounted. Always check clearance to the enclosure door.
• Module Guide Card Fractures: On older systems, plastic card guides can become brittle over time. When executing the transfer, care must be taken to not crack or stress the card slots.
• Removing Redundant Power Cables: If your install uses the 1756-CPR2 redundant cable, the routing space at the far left is tight. Dropping or bending the locking pins of the 13-pin connector can ruin the power routing interface.

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Step-by-Step Replacement Procedure

Follow this procedural standard to execute a replacement of a 1756-A13 chassis.

Phase 1: Pre-Work and Safety Isolation

1. Perform Backup: Connect to the active ControlLogix controller using Studio 5000 / RSLogix 5000 and perform a complete upload of the program tag databases, force values, and volatile memory configurations. Save this copy as an offline recovery image.
2. Disconnect Main Power: Turn off and lock out (LOTO) the electrical supply breaker supplying the chassis power supply (1756-PA72/PB75). Verify with a calibrated digital multimeter that no AC or DC potential exists at the terminal block inputs.
3. Label Interconnecting Cables: Physically label every terminal block (RTB) and Ethernet/ControlNet cable with its respective slot position (Slots 0 to 12). Document the physical layout of the modules for verification.

Phase 2: Removing Modules and Power Supply

4. Extract the Power Supply:
   • Unscrew the primary input wiring connector block.
   • Using a screwdriver, loosen the mounting screws located on the top and bottom of the power supply chassis.
   • Slide the power supply up and forward, pulling it off the mounting tabs.
5. Remove Installed Modules:
   • Loosen the RTB (Removable Terminal Block) retaining screws on the front of I/O modules and gently pull them out, leaving the field wires attached to the blocks. Do not tug on the copper strands.
   • For field bus cables (such as RJ45 Ethernet leads), release the latching clip and ease the cable out of the socket.
   • Open the module release latches (located at the top and bottom of each module's faceplate) by squeezing them inward.
   • Slide each module smoothly out of the chassis guides. Lay the modules on a static-dissipative ESD mat.

          [SQUEEZE LATCH] <--- Top of Module
                 |
                 v
        [================]
        [  Module Face   ] ---> Slide Module out of Card Guide
        [================]
                 ^
                 |
          [SQUEEZE LATCH] <--- Bottom of Module

Phase 3: Physical Chassis Swap

6. Unmount the Damaged Chassis:
   • Disconnect the green/yellow functional ground copper strap from the grounding stud located on the bottom flange of the chassis frame.
   • Unscrew the four M6 (or 1/4 inch) mounting bolts on the corners of the chassis plate.
   • Carefully hoist the empty chassis out of the enclosure panel.
7. Prepare and Install the New Chassis:
   • Inspect the backplane connector pins of the new 1756-A13 chassis to ensure no debris or bent metal pins reside inside slots 0 through 12.
   • Position the new chassis onto the mounting panel space and thread the four corner bolts. Torque to 1.4 N-m (12 lb-in).
   • Reconnect the functional ground strap to the chassis ground stud. Ensure the connection is metal-to-metal (scrape off any paint around the grounding plane contact point if necessary).

Phase 4: Reassembly and Testing

8. Reinstall Power Supply and Modules:
   • Slide the power supply back onto the chassis guide bracket and screw it into place. Re-attach the wiring.
   • Slide every module back into its exact original slot index (0 to 12). Gently push the module back until the upper and lower latches snap-lock firmly into place.
   • Reinsert the labeled Removable Terminal Blocks (RTBs) and secure their retaining screws.
   • Reconnect all communication cables (Ethernet, ControlNet, etc.).
9. Commissioning and Initial Diagnostics:
   • Apply primary AC/DC input power to the power supply.
   • Observe the power supply LED. It must indicate steady green (OK).
   • Verify each module completes its power-on self-test (POST). Typically, all module LEDs will cycle, then transition to their designated states.
   • Ensure the CPU returns to 'Run' or 'Remote Run' mode, confirming no module connection loss (I/O LED blinking indicates connection issues). Use Studio 5000 to check for module connection errors.

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Frequently Asked Questions

Q1: Can I replace a Series A 1756-A13 with a Series C chassis without changing system software?

Yes. The 1756-A13 is a passive mechanical hardware backplane. The programming software (Studio 5000) does not look detect nor poll for the chassis Series index. The controller configuration profile only tracks the slot count (13 slots), meaning no modifications are needed in your RSLogix / Studio 5000 logic configuration to implement the swap.

Q2: Why is proper grounding of the 1756-A13 chassis crucial?

The modules installed in a Logix chassis rely entirely on physical contact with the metal backplane chassis frame through their grounded latch mechanism to discharge high-frequency electrical noise (EMI) and operational electrostatic buildups. Poor grounding can cause inter-module communications errors, spontaneous module lockups, and CPU faults.

Q3: When should I choose the 1756-A13XT over the standard 1756-A13?

If your system cabinet is deployed in non-climate-controlled fields, wastewater treatment facilities, chemical processing zones, or oil/gas collection platforms, the 1756-A13XT is required. The "XT" version specifies conformal coating on the internal backplane circuit board, protecting physical circuits from moisture, fungus, and atmospheric corrosive gases.

Q4: Can I use different models of processors side-by-side in a single 13-slot chassis?

Yes. Standard ControlLogix multi-processing architecture allows you to mount multiple processors (e.g., placing two 1756-L73 controllers or combining a 1756-L83E and a 1756-L72) in any slots within the same 1756-A13 chassis. They communicate with one another using the shared backplane bus.

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Related Products & Families

To complete your upgrade or sustain inventory integrity, consider examining the standard compatible hardware in the ControlLogix family:

• Controllers: 1756-L81E, 1756-L82E, 1756-L83E (ControlLogix 5580 active generation controllers)
• Power Supplies: 1756-PA75, 1756-PB75 (Standard non-redundant supply modules)
• EtherNet Modules: 1756-EN2T, 1756-EN3TR, 1756-EN4TR (High-performance communications adapters)
• Digital I/O: 1756-IB16D (Diagnostically enabled DC input modules), 1756-OB16E (Electronic fused outputs)

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Need Help?

Replacing or upgrading critical industrial hardware demands high quality components to eliminate unplanned plant downtime. At Palm Parts Solution, we supply a comprehensive range of new, high-quality refurbished, and hard-to-find surplus Allen-Bradley ControlLogix components, including the 1756-A13 13-slot legacy and current series chassis.

All our components undergo extensive testing and are backed by our industry-grade warranty, giving you peace of mind that your migration will be seamless. Contact our engineering support team today to check inventory or request an immediate quote.