Allen-Bradley 1756-PA75 — ControlLogix Power Supply Buying Guide

By Abdullah Zahid
14 min read
Allen-Bradley 1756-PA75 ControlLogix AC power supply module mounted in 1756 chassis for industrial automation control panel

Allen-Bradley 1756-PA75 ControlLogix AC Power Supply — Specs, Selection Guide, and Expert Review

If you are specifying or replacing a power supply for a 1756 ControlLogix chassis, the Allen-Bradley 1756-PA75 is one of the first catalog numbers that comes up — and for good reason. It accepts a wide 85–265 VAC input, delivers up to 75 W of backplane power across four DC voltage rails, and carries UL, CE, CSA, and marine approvals that satisfy most North American and international project requirements. The decision usually comes down to three questions: Is your mains source AC? Is 75 W enough for your module load? And do standard industrial conditions apply? If the answer to all three is yes, this is almost certainly your supply.

If you have already confirmed this is the right part, check current pricing and availability at LeadTime.ca — ships worldwide.

Who Should Buy the Allen-Bradley 1756-PA75 — and Who Shouldn't

The 1756-PA75 is the right choice if all of the following apply to your project:

  • You are working with a 1756 ControlLogix chassis — this supply does not fit CompactLogix, MicroLogix, or any other platform.
  • Your panel mains supply is AC in the 85–265 VAC range at 47–63 Hz — either 120 V or 230 V installations are covered by a single catalog number.
  • Your total backplane load across all planned modules is within the 75 W capacity and individual rail current limits of this supply.
  • Your operating environment falls within 0–60 °C and standard industrial pollution conditions — no corrosive atmosphere or immersion requirement.
  • Your project compliance requirements are satisfied by UL, CE, CSA, KC, marine, NRTL, RCM, and CCC approvals.

If your system runs on DC control power, operates in a harsh or corrosive environment requiring a conformal-coated variant, or carries a backplane load that pushes beyond 75 W with room for expansion, you should evaluate the 1756-PB75 for DC input, the 1756-PA75K for conformal-coated protection, or a higher-capacity supply before ordering.

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What the Allen-Bradley 1756-PA75 Actually Does in a ControlLogix System

The 1756-PA75 is a chassis-mounted AC power supply module that converts plant mains power — anywhere from 85 to 265 VAC at 47–63 Hz — into the regulated DC voltages the ControlLogix backplane needs to run. It sits at the left end of a 1756 chassis and simultaneously supplies four backplane rails: 1.2 V DC at approximately 1.5 A, 3.3 V DC at approximately 4 A, 5 V DC at approximately 13 A, and 24 V DC at approximately 1.75 A. The total output budget across all rails is 75 W.

Every module installed in the chassis — the CPU, communication adapters, analog and digital I/O cards, and motion modules — draws its operating power from these rails through the backplane connector. The power supply is not a field-power source for field devices; it exists solely to keep the electronics inside the chassis alive and stable. Front-panel status LEDs indicate whether the supply is operating normally or has entered a fault condition, giving maintenance technicians an immediate visual reference without needing to open software.

The open-style housing means the 1756-PA75 requires a panel or enclosure around it — it is not rated for standalone or exposed installation. This is standard practice for ControlLogix hardware and aligns with typical industrial control panel builds.

Typical System Architecture for the 1756-PA75

The 1756-PA75 sits between the plant AC distribution panel and the ControlLogix backplane, converting mains voltage into the regulated low-voltage DC rails the system depends on. A typical deployment looks like this:

  • Plant AC mains (120 VAC or 230 VAC) feeds a dedicated circuit with upstream overcurrent protection and a disconnecting means inside the control panel.
  • The protected AC feed connects to the 1756-PA75 input terminals at the left end of the 1756 chassis.
  • The 1756-PA75 converts and regulates that input into 1.2 V, 3.3 V, 5 V, and 24 V DC rails distributed across the chassis backplane.
  • All modules inserted into the chassis — including the ControlLogix CPU, EtherNet/IP or ControlNet communication modules, and I/O modules — draw their operating power directly from those backplane rails.
  • For larger systems with additional I/O racks, each remote 1756 chassis requires its own power supply, and the same sizing calculation applies to each.

Industries and Applications Where the 1756-PA75 Is Specified

The 1756-PA75 appears in virtually every industry that runs ControlLogix as its primary control platform. Process plants — oil and gas facilities, chemical and petrochemical operations, food and beverage production lines, and water and wastewater treatment systems — routinely specify this supply for main control racks that run on standard 120 or 230 VAC distribution. The 0–60 °C operating range and the breadth of certifications (including marine approval) make it a natural fit for regulated environments where compliance documentation matters.

In manufacturing, the 1756-PA75 is common in machine tool control panels, automotive assembly systems, and large packaging lines where a ControlLogix rack handles motion and I/O simultaneously. OEM machine builders shipping equipment globally rely on the 85–265 VAC input range to avoid designing separate power supply configurations for North American and European installations — a single catalog number covers both.

Maintenance and MRO teams in mining, metals, and power generation facilities frequently stock the 1756-PA75 as a critical spare. When a power supply fails, the consequence is a full rack outage, so fast replacement with an already-validated part number is a strong operational argument for keeping one on the shelf.

Application Typical Deployment
Plant DCS/PLC upgrade Main control rack running on 120/240 VAC with mixed CPU, comm, and I/O modules
Failed supply replacement Drop-in swap for existing 1756-PA75 in a running ControlLogix chassis to restore rack power
OEM global machine build Universal AC input eliminates region-specific supply variants for worldwide machine shipments
MRO critical spares Stocked unit for fast replacement in high-uptime ControlLogix systems
I/O expansion rack Separate 1756 chassis with its own 1756-PA75 added to extend I/O or motion capacity
Marine and regulated facilities Systems requiring documented marine, UL, CSA, and CE compliance in the same supply

Key Specifications and Variant Comparison for the 1756-PA75

Specification Value
Catalog Number 1756-PA75
Input Voltage Range 85–265 VAC
Input Frequency 47–63 Hz
Maximum Output Power 75 W backplane power
Backplane Output — 5 V Approx. 13 A
Backplane Output — 24 V Approx. 1.75 A
Backplane Output — 3.3 V Approx. 4 A
Backplane Output — 1.2 V Approx. 1.5 A
Operating Temperature 0–60 °C (32–140 °F)
Approvals UL, CE, CSA, KC, Marine, NRTL, RCM, CCC

Full technical specifications are available on the product page at LeadTime.ca.

1756-PA75 vs. Key ControlLogix Power Supply Variants

Model Input Type Output Power Notable Difference vs. 1756-PA75
1756-PA75 85–265 VAC 75 W Standard AC supply — this model
1756-PA75K 85–265 VAC 75 W Conformal-coated for harsh/corrosive environments
1756-PA72 85–265 VAC 72 W Lower output capacity; earlier generation
1756-PB75 19.2–31.2 VDC 75 W DC input for DC control power architectures
1756-PB72 19.2–31.2 VDC 72 W Lower-capacity DC input variant
1756-PH75 High-voltage DC input 75 W High-voltage DC input for specific applications

If your panel runs on DC control power rather than AC mains, the 1756-PB75 is the direct DC-input equivalent — confirm your input power type and check all available variants at LeadTime.ca.

Expert Verdict: Is the Allen-Bradley 1756-PA75 Right for Your Project?

The 1756-PA75 earns its place as the default AC power supply for ControlLogix systems because it solves the most common configuration cleanly. The 85–265 VAC input range is genuinely useful — it means the same catalog number works in a Canadian plant running 120 VAC distribution and on a machine shipped to a European facility running 230 VAC, without any hardware change. The 75 W output is sufficient for the majority of small to mid-size ControlLogix racks carrying a standard mix of CPU, communication, and I/O modules. The approval list — UL, CE, CSA, marine, NRTL, RCM, CCC — is broad enough to satisfy most regulated project documentation requirements without chasing supplemental certifications. Controls engineers specifying a new main rack or maintenance teams replacing a failed supply in an existing validated system will find this is the correct and defensible part number for standard AC-powered, standard-environment applications.

The limits are real and worth stating plainly. If your control power distribution is DC-based — increasingly common in facilities that standardize on 24 VDC control power for safety or battery backup reasons — the 1756-PA75 is the wrong family entirely; look at the 1756-PB75 instead. If your installation environment involves condensation, corrosive vapors, or contamination levels that exceed standard industrial classification, the 1756-PA75K with conformal coating is the correct choice, not a workaround. And if your module list — particularly if it includes motion axes, high-density analog cards, or multiple communication modules — pushes the backplane load calculation close to or beyond 75 W, do that arithmetic carefully before locking in this supply. A chassis that is marginally over budget today becomes a reliability problem during future expansion.

From a procurement standpoint, the 1756-PA75 is a well-established catalog number with established distribution channels globally. Stock levels can shift with broader ControlLogix supply chain conditions, and lead times from authorized channels can range from same-week availability when stock is healthy to several weeks when demand spikes. Working with a specialist automation distributor gives you a real advantage here — the ability to cross-check inventory across multiple sources, validate that the series and coating variant match your plant documentation, and identify alternatives before a project schedule is at risk. View current stock status and pricing for the 1756-PA75 at LeadTime.ca — we ship worldwide.

For volume pricing or to confirm lead time before committing to a build schedule, contact the LeadTime.ca team directly — we ship worldwide.

What Engineers Need to Know Before Ordering the 1756-PA75

Model-specific community discussion for the 1756-PA75 is sparse — which is, in practice, a meaningful data point. Mature, reliable components in mainstream PLC families rarely generate complaint threads. Engineers on r/PLC, PLCTalk, PLCS.net, and MrPLC tend to discuss ControlLogix power supplies at the family level rather than flagging issues with specific catalog numbers. When the 1756-PA75 does come up, it surfaces in the context of ordering questions and sizing decisions, not failure reports. The absence of recurring fault patterns in community forums aligns with what you would expect from a standard, well-supported industrial component with a long field history.

Where community discussions do flag risk, it is consistently about ordering the wrong variant — not about the unit failing in service. The most commonly cited confusion points are mixing up the AC-input PA series with the DC-input PB series when a BOM is copied from a different project, and failing to distinguish between the standard 1756-PA75 and the conformal-coated 1756-PA75K when specifying for environments that technically require the coated version. A second recurring theme is backplane load calculation errors — engineers who estimate rather than calculate module current draws and discover mid-commissioning that the 75 W budget is tighter than expected. None of these are defects in the product; they are specification and procurement errors that good pre-order discipline prevents.

When community data is thin and the part is critical to system uptime, the most practical resource is a specialist distributor who has handled enough ControlLogix configurations to recognize the common mis-specification patterns. If you are replacing a unit in a validated system, confirm series and coating match exactly against your existing documentation before ordering. If you are sizing a new rack, use the official Rockwell power calculation method — do not estimate. And if you are unsure whether your environment qualifies for the standard version or requires the K variant, that is a conversation worth having before the order is placed, not after the supply arrives on site.

Wiring and Installation Overview for the 1756-PA75

The following points summarize the key requirements for installing and commissioning the 1756-PA75. For full procedures, refer to the Allen-Bradley 1756-PA75 installation instructions and the ControlLogix system installation manual from Rockwell Automation.

  • The 1756-PA75 mounts at the left end of the 1756 chassis only — confirm chassis positioning and secure it with the top and bottom mounting screws before connecting any wiring.
  • Connect AC line, neutral, and protective earth conductors to the labeled input terminals using conductor sizes and torque values specified in the installation manual; missing or undersized protective earth is a safety and compliance risk.
  • Upstream overcurrent protection and a suitable disconnecting means are required and must be installed by the user — the 1756-PA75 does not include internal branch circuit protection.
  • Secure the AC power cable using the retention feature or cable ties to prevent mechanical strain on the input terminals.
  • After energizing, verify all front-panel status LEDs indicate normal operation before inserting or cycling any chassis modules — a fault LED at power-up indicates a wiring, load, or supply issue that must be resolved before proceeding.

Compatible Modules and System Expansion

The 1756-PA75 provides backplane power to any module installed in a compatible 1756 ControlLogix chassis. The following represent the primary module categories it supports in typical system builds:

  • ControlLogix CPUs (1756-L series) — the primary processor drawing from the 5 V and 3.3 V rails.
  • EtherNet/IP communication modules (1756-EN series) — network bridge modules that contribute meaningfully to the 5 V rail load.
  • ControlNet, DeviceNet, and serial communication modules (1756-CN, 1756-DNB, 1756-MVI series) — additional communication loads to include in the backplane budget.
  • Digital and analog I/O modules (1756-IB, 1756-OB, 1756-IF, 1756-OF series) — field interface modules whose combined current draw frequently defines whether 75 W is adequate.
  • Servo and motion control modules (1756-M series) — high-power-draw modules that require careful inclusion in the load calculation, as a few of these can consume a significant share of the 75 W budget.

Wrong-Part Prevention Checklist for the 1756-PA75

Before placing any order for the Allen-Bradley 1756-PA75, work through every item on this checklist. These checks apply equally to new builds and to replacement orders in existing systems.

  1. Confirm the controller platform is ControlLogix with a 1756 chassis (this supply does not fit CompactLogix, MicroLogix, etc.).
  2. Verify that plant power at the panel is AC in the 85–265 VAC range; do not use this unit on DC mains.
  3. Calculate total backplane current for all planned modules and confirm it is within the 75 W / rail current limits of the 1756-PA75.
  4. Check environmental conditions (temperature, humidity, contamination) and decide if a conformal-coated "K" variant is needed instead.
  5. Confirm chassis size and that this will be mounted on the left end of the chassis as the primary supply.
  6. Ensure compliance and approvals (UL, CE, CSA, marine, etc.) match project and regional requirements.
  7. If you need redundant power supplies, verify that the chosen chassis and system design support the intended redundancy scheme.
  8. For replacements, match series and coating (standard vs K) where validated by your plant standards or validation rules.

If any item on this checklist raises a question before you order, contact the LeadTime.ca team — we can validate compatibility against your chassis configuration and module list before the order is placed.

Frequently Asked Questions

Can the 1756-PA75 run on both 120 VAC and 230 VAC without any modification?

Yes. The 1756-PA75 accepts 85–265 VAC at 47–63 Hz, which covers both 120 V North American and 230 V European and international mains distributions on a single catalog number. No jumper, tap change, or hardware modification is required. This is one of the primary reasons OEM machine builders standardize on this supply for globally shipped equipment.

How do I confirm that 75 W is enough for my specific ControlLogix chassis?

Use the official Rockwell Automation power calculation method: obtain the backplane current draw for each module you plan to install from its individual datasheet, sum the currents on each voltage rail (1.2 V, 3.3 V, 5 V, and 24 V), and compare the totals against the per-rail limits and 75 W total capacity of the 1756-PA75. Allow headroom for any modules you expect to add in future expansion. If the total approaches or exceeds 75 W, evaluate a higher-capacity supply or split the I/O across two chassis with separate power supplies.

What is the difference between the 1756-PA75 and the 1756-PA75K?

Both models share identical electrical ratings — 85–265 VAC input, 75 W backplane output, and the same approval set. The 1756-PA75K adds a conformal coating to the PCB assembly, providing protection against moisture, condensation, and corrosive or contaminating atmospheres. If your installation environment involves any of these conditions, the K variant is the correct specification. For replacements in validated systems, match the variant — standard or K — exactly to what is currently installed unless your change control process explicitly authorizes a substitution.

Does the 1756-PA75 support redundant power supply configurations?

The 1756-PA75 is a single, non-redundant power supply. If your application requires power supply redundancy, verify whether your specific 1756 chassis model and system architecture support a redundant supply scheme, and confirm which Allen-Bradley catalog numbers are validated for that configuration. Not all 1756 chassis sizes support dual-supply redundancy in the same way, and the intended redundancy scheme must be confirmed against the system design documentation before ordering.

What should I check first if a ControlLogix rack powered by a 1756-PA75 fails to power up?

Start with the supply input: confirm that AC voltage in the 85–265 VAC range is present at the input terminals and that upstream overcurrent protection has not tripped. Next, inspect the terminal connections for loose conductors or missing protective earth. Check the front-panel status LEDs on the 1756-PA75 — a fault indication points to a supply or backplane load issue rather than an upstream problem. If input power is confirmed and the supply LED indicates a fault, verify that the total backplane load of installed modules is within the 75 W rating. If the supply appears healthy but modules are not initializing, the issue may be with individual modules or the chassis backplane rather than the power supply itself.

Why Order the Allen-Bradley 1756-PA75 From LeadTime.ca

  • LeadTime.ca ships worldwide — no geographic restrictions on quoting or fulfillment.
  • Specialist automation distributor with direct familiarity with ControlLogix hardware configurations, not a general electronics broker.
  • Real-time inventory checking across multiple sourcing channels, including new authorized stock and vetted surplus, to address lead time gaps.
  • Pre-order compatibility validation available — confirm the right variant (standard vs K, correct series) against your chassis and module list before the order is placed.
  • Volume pricing and project-level quoting available for procurement teams building BOMs or stocking critical spares.

At-a-Glance Summary: Allen-Bradley 1756-PA75

  • AC input range: 85–265 VAC at 47–63 Hz — covers 120 V and 230 V mains on a single catalog number.
  • Maximum backplane output: 75 W total across 1.2 V, 3.3 V, 5 V, and 24 V DC rails.
  • 5 V rail output: approximately 13 A — typically the dominant rail for CPU and communication module loads.
  • Operating temperature: 0–60 °C, suitable for standard industrial control panel environments.
  • Approvals: UL, CE, CSA, KC, Marine, NRTL, RCM, CCC — broad compliance for regulated applications.
  • Platform: 1756 ControlLogix chassis only — not compatible with CompactLogix, MicroLogix, or other families.
  • Mounting position: left end of the 1756 chassis, open-style, requires panel enclosure.
  • Key variant to know: 1756-PA75K adds conformal coating for harsh environments; 1756-PB75 is the DC-input equivalent.
  • Primary ordering risk: confirming AC vs DC input type and verifying total backplane load before placing the order.

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