Allen-Bradley 1756 ControlLogix Modules – 1756-A7K

Technical Dossier

Product Details And Specifications

Allen-Bradley 1756 ControlLogix Series Technical Notes

The Evolution of 1756 ControlLogix Architecture

The ControlLogix architecture has passed through three distinct engineering generations since its commercial launch. The original Series A chassis and controllers (circa 1997–2004) established the 1756 backplane standard and introduced tag-based programming via RSLogix 5000. Series B hardware (2004–2012) brought enhanced diagnostics, increased memory ceilings on L6x controllers, and expanded EtherNet/IP native support. The current generation — anchored by L7x and L8x controllers — introduced 64-bit processing, SIL 2 safety integration via GuardLogix, and CIP Security for network-layer authentication.

Compatibility across generations is a critical operational concern. Series A chassis are electrically compatible with current-generation modules but are limited by backplane power budgets that predate high-draw communication modules. The 1756-A7K chassis is available in both standard and conformal-coated (K-suffix) variants; the K designation indicates a conformal coating applied to the PCB assembly for operation in environments with elevated humidity, condensation, or airborne contaminants — a specification requirement common in coastal chemical plants and offshore installations.

1756 ControlLogix Full Catalog & Functionalities (SKU List)

Chassis

• 1756-A4: 4-slot ControlLogix chassis, standard backplane, no conformal coat
• 1756-A7: 7-slot ControlLogix chassis, standard backplane configuration
• 1756-A7K: 7-slot ControlLogix chassis, conformal-coated PCB for harsh environments
• 1756-A10: 10-slot chassis, mid-density panel builds, standard backplane
• 1756-A13: 13-slot chassis, high I/O density installations
• 1756-A17: 17-slot chassis, maximum slot count for large-scale control nodes

Controllers (CPU)

• 1756-L71: ControlLogix 5570 controller, 2 MB memory, single Ethernet port
• 1756-L72: ControlLogix 5570 controller, 4 MB memory, enhanced task capacity
• 1756-L73: ControlLogix 5570 controller, 8 MB memory, high-task-count applications
• 1756-L74: ControlLogix 5570 controller, 16 MB memory, large program storage
• 1756-L75: ControlLogix 5570 controller, 32 MB memory, maximum L7x capacity
• 1756-L83E: ControlLogix 5580 controller, 3 MB memory, dual Ethernet, CIP Security
• 1756-L85E: ControlLogix 5580 controller, 40 MB memory, highest L8x performance tier

Digital I/O Modules (DI / DO)

• 1756-IB16: 16-point 24VDC sinking digital input module
• 1756-IB32: 32-point 24VDC sinking digital input, high-density panel wiring
• 1756-OB16E: 16-point 24VDC electronically fused digital output module
• 1756-OB32: 32-point 24VDC sourcing digital output, high-density

Analog I/O Modules (AI / AO)

• 1756-IF16: 16-channel analog input, 4–20 mA / 0–10V, 16-bit resolution
• 1756-OF8: 8-channel analog output, 4–20 mA / voltage, isolated channels

Communication Adapters

• 1756-EN2T: EtherNet/IP communication module, single copper port, 100 Mbps
• 1756-EN2TR: EtherNet/IP module with dual-port DLR ring topology support
• 1756-CN2: ControlNet communication module, coax media, redundant media capable
• 1756-DNB: DeviceNet scanner module, master node for DeviceNet field devices

Power Supplies

• 1756-PA72: 85–265VAC input power supply, 13A backplane output
• 1756-PB72: 18–32VDC input power supply, 13A backplane output
• 1756-PSCA2: Power supply chassis adapter for redundant power configurations

Sourcing Hard-to-Find & Obsolete 1756 ControlLogix Parts

DriveKNMS operates as a specialist distributor for the full 1756 ControlLogix lifecycle, with particular depth in discontinued and allocation-constrained part numbers. The L6x controller family (1756-L61, 1756-L62, 1756-L63, 1756-L64, 1756-L65) reached End of Life status and is no longer manufactured by Rockwell Automation. Facilities that have not migrated to L7x or L8x architecture require a reliable secondary market source for these controllers to maintain production continuity.

Quality Control for the 1756 ControlLogix Range

The 1756 backplane architecture presents specific test requirements that differ from standard I/O module verification. Each chassis supplied by DriveKNMS undergoes backplane continuity testing across all slot connectors using a dedicated 1756 backplane analyzer, verifying signal integrity on the 200 MB/s data bus, power rail voltage tolerances (±2% on 5VDC and 24VDC rails), and slot-to-slot isolation resistance. Conformal-coated variants such as the 1756-A7K are additionally inspected under UV light to verify coating coverage uniformity across the PCB surface, with particular attention to connector bodies and high-voltage isolation zones.

Communication modules (1756-EN2T, 1756-EN2TR, 1756-CN2) are tested under live network load using protocol analyzers to verify CIP connection establishment, packet error rates below 0.001%, and correct MAC/IP address assignment. Controller modules are powered through a full boot cycle, firmware version is recorded, and memory integrity is verified via a structured read/write test across the full addressable memory range. All test results are logged to a serialized inspection record that ships with each unit.