When a ControlLogix Chassis Loses Backplane Power
A stopped ControlLogix line rarely announces itself. Modules go dark, I/O drops out, and production halts while technicians trace the fault. The Allen-Bradley 1756-PA75 is the standard power supply that prevents that scenario by feeding clean backplane power to every module in the chassis. It installs in the dedicated left-most slot of a 1756 chassis and accepts a wide 85-265VAC input, so it tolerates real-world voltage swings on plant floors.
What the 1756-PA75 Delivers
The 1756-PA75 converts an external AC supply into regulated backplane power. Its input range of 85-265VAC with 47-63 Hz frequency covers nominal 120VAC and 240VAC systems. Output capacity is 4 A at 3.3VDC, 13 A at 5.1VDC, and 2.8 A at 24VDC, with a total power rating of 75 W across 0 to +60 °C. A hold-up time of 2 cycles at 85VAC, 6 cycles at 120VAC, and 20 cycles at 220VAC keeps modules alive through brief interruptions. Isolation voltage is 250 V continuous, and maximum inrush current is 30 A.
Key Specifications
| Parameter | Value |
|---|---|
| Input Voltage Range | 85-265VAC |
| Input Frequency | 47-63 Hz |
| Power Output | 75 W at 60 °C |
| Current Capacity | 4 A at 3.3VDC; 13 A at 5.1VDC; 2.8 A at 24VDC |
| Isolation Voltage | 250 V continuous |
| Max Inrush Current | 30 A |
| Operating Temperature | 0-60 °C (32-140 °F) |
| Weight | 0.95 kg (2.10 lb) |
Solving Installation and Compatibility Pain Points
Mounting Position
The 1756-PA75 must sit in the left-most slot of the chassis. This position is dedicated to power, so plan rack layout before wiring. The unit is compatible with 1756-A4, 1756-A7, 1756-A10, 1756-A13, and 1756-A17 chassis across Series B and Series C.
Environmental Limits
The supply operates in Pollution Level 2 industrial environments and overvoltage Category II applications per IEC 60664-1. It runs at altitudes up to 2000 meters without derating. A non-replaceable fuse guards against short-circuit fire hazards, so always verify input wiring before energizing.
Configuration Requirement
The 1756-PA75 requires hardware configuration. Confirm the chassis slot assignment and input voltage setting before commissioning to avoid startup faults.
Applications Where This Supply Earns Its Place
Oil and gas facilities, water treatment plants, and manufacturing cells rely on ControlLogix for process control. The 1756-PA75 suits these settings because its wide input range handles unstable plant power, and its hold-up time bridges brief outages. For retrofit projects, matching the exact supply to the chassis series prevents backplane faults. When a line is down, fast access to the right spare matters. Oil AutoTech stocks ready-to-ship ControlLogix spares and offers hands-on technical selection help to confirm chassis compatibility before dispatch.
Maintenance and Reliability
Inspect the supply periodically for dust buildup and secure connections. Verify input voltage stays within 85-265VAC. Because the fuse is non-replaceable, a blown fuse means replacing the unit. Keep spare 1756-PA75 supplies on hand for critical lines. Fast dispatch, worldwide delivery keeps production moving when downtime is not an option.
Verify Before You Order
Confirm your chassis model, series, and slot position. Check that your input supply matches 85-265VAC at 47-63 Hz. Please verify current lifecycle status and availability with Oil AutoTech before ordering. Contact Oil AutoTech today for pricing and availability.
