Product Overview

The Allen-Bradley 1756-PA72K​ is a 75-watt AC-input power supply module engineered for Rockwell Automation’s ControlLogix® 1756 series programmable automation controller chassis. It is designed to occupy Slot 0 (the leftmost position) of any standard 1756 chassis—including the 1756-A4, A7, A10, A13, and A17—where it converts facility AC mains (or DC in the specified range) into the multiple regulated DC voltages required by the ControlLogix backplane: 5.1 V DC for logic circuits, 3.3 V DC, 1.2 V DC, and 24 V DC for auxiliary/field power. The “K” suffix on the Allen-Bradley 1756-PA72K​ denotes that the printed circuit board assemblies have been processed with a conformal coating—a thin polymeric film that protects against moisture, salt spray, condensation, and airborne contaminants classified under ISA-S71.04G1 through G3 severity levels. This makes the Allen-Bradley 1756-PA72K​ the preferred choice for pulp & paper mills, wastewater treatment plants, coastal marine installations, and chemical processing areas where uncoated electronics would be vulnerable to premature corrosion or dendrite formation.The Allen-Bradley 1756-PA72K​ accepts a universal input range of 85–265 V AC (47–63 Hz) or 85–300 V DC, eliminating the need for voltage-select jumpers and simplifying global deployment. It delivers up to 10 A on the 5.1 V backplane rail (total 75 W maximum across all outputs) and supports Remove and Insert Under Power (RIUP) for hot-swap replacement in a running system. When higher availability is required, two 1756-PA72K units can be deployed in an N+1 redundant configuration using a 1756-RA or 1756-RM2 redundancy adapter module and the appropriate 1756-CPR2 cable set. LED status indicators on the front of the Allen-Bradley 1756-PA72K​ provide at-a-glance confirmation of AC presence (AC OK), DC output health (DC OK), and fault conditions, assisting maintenance personnel in rapid diagnostics without test equipment. Fully compatible with all Logix5000™ controllers and 1756 I/O/communication modules, the Allen-Bradley 1756-PA72K​ is the foundational power element that ensures stable, noise-immune operation of the entire ControlLogix control system.

Technical Specifications

Product Model | 1756-PA72KManufacturer | Rockwell Automation / Allen-BradleyProduct Type | ControlLogix 75W AC-Input Chassis Power Supply Module (Conformal Coated)Series | Allen-Bradley 1756 ControlLogixInput Voltage (AC) | 85–265 V AC, 47–63 Hz, single phaseInput Voltage (DC) | 85–300 V DC (acceptable on AC terminals L1/L2/N)Rated Output Power | 75 W totalBackplane Output – 5.1 V DC | 10 A max (primary logic rail)Backplane Output – 3.3 V DC | 4 A maxBackplane Output – 1.2 V DC | 1.5 A maxBackplane Output – 24 V DC | 2.8 A max (auxiliary/user-sourced)Inrush Current (max) | 20 A peak, limited by internal NTCProtection Features | Overvoltage, undervoltage, overcurrent, overtemperature; hiccup-mode recoveryHold-Up Time | > 20 ms @ full load (typical, after AC loss)Efficiency | Typically 80–84 % @ 120/240 V AC full loadOperating Temperature | 0 °C to +60 °C (32 °F to 140 °F)Storage Temperature | -40 °C to +85 °CRelative Humidity | 5 % to 95 % non-condensing (ISA-S71.04 G3 capable with conformal coat)Conformal Coating | Yes – urethane-based, per IPC-CC-830 / MIL-I-46058Agency Approvals | UL Listed, cULus, CE, C-Tick, KC, FM Class I Div 2 (with appropriate system enclosure)Chassis Slot Requirement | Slot 0 only (leftmost slot of 1756 chassis)Redundancy Support | Yes – with 1756-RA / 1756-RM2 + 1756-CPR2

Main Features and Advantages

The most distinguishing feature of the Allen-Bradley 1756-PA72K​ versus the standard 1756-PA72 is its full conformal coating. In pulp & paper bleach plants, coastal offshore platforms, or metal pickling lines where chlorine, hydrogen sulfide, or salt-laden air is present, uncoated PCBs can develop conductive filaments (dendrites) that lead to intermittent shorts and eventual module failure. The Allen-Bradley 1756-PA72K​ mitigates this failure mode by sealing solder joints, traces, and component bodies beneath a certified insulating coating—extending Mean Time Between Failure (MTBF) and reducing unplanned downtime in harsh-environment installations. The coating is applied after functional test and is fully compatible with the module’s thermal dissipation requirements.Universal input capability is another practical advantage. The Allen-Bradley 1756-PA72K​ auto-adapts to any global single-phase AC mains from 85 V to 265 V without manual reconfiguration, and will even operate from a 24 V DC nominal source in the 85–300 V DC range (though not intended as a primary DC-rated supply). This flexibility simplifies spare-parts inventory for multinational OEMs and system integrators who build machinery for export markets.For high-availability processes, the Allen-Bradley 1756-PA72K​ supports N+1 redundancy: two units feed a redundancy adapter which presents a single clean 5 V / 24 V rail to the chassis backplane. If one supply fails or is removed for service, the second continues powering the rack without interruption—a critical capability in continuous-process industries. The module’s RIUP design means the Allen-Bradley 1756-PA72K​ can be replaced live; the chassis remains powered either by a redundant partner or (in non-redundant setups) by briefly bridging power during a controlled maintenance window. Front-panel LEDs—AC OK (green), DC OK (green), and Fault (red)—together with the module-health bit readable in the controller, give both local and remote visibility into power system status, enabling proactive maintenance before a total loss of control power occurs.

Application Field

The Allen-Bradley 1756-PA72K​ is specified wherever a ControlLogix system must be deployed in environmentally challenging conditions that exceed the corrosion resistance of standard (uncoated) power supplies. In municipal water and wastewater treatment plants—particularly in pump stations with high humidity and occasional hydrogen sulfide exposure—the Allen-Bradley 1756-PA72K​ safeguards the control system’s power backbone. Similarly, in food & beverage canneries and breweries where periodic high-pressure washdown and caustic cleaning agents create corrosive atmospheres, the conformal-coated version is routinely selected to match coated processors and I/O modules elsewhere in the panel.Offshore and marine applications also favor the Allen-Bradley 1756-PA72K: salt-spray-laden air in engine rooms or topside enclosures accelerates degradation of bare electronics, and the “K”-suffix coating provides the necessary defense. In chemical processing, especially chlor-alkali, fertilizer, or smelting operations, the coated power supply is often mandated by site engineering standards as part of a G3-corrosivity-rated control panel specification. Even in less aggressive environments, some asset owners standardize on the Allen-Bradley 1756-PA72K​ across all ControlLogix racks to achieve uniformity and eliminate the risk of accidentally installing an uncoated unit in a sensitive area. For any ControlLogix-based system where long-term power integrity and environmental resilience are priorities, the Allen-Bradley 1756-PA72K​ delivers dependable, globally-compatible chassis power with the added assurance of conformal coating protection.