When Downtime Strikes, Your Power Supply Is the First Suspect
A CompactLogix chassis that suddenly loses backplane power can halt an entire production line. The Allen-Bradley 1769-PA4 is the I/O power supply engineered to keep that backplane energized. It distributes power to 1769 Compact I/O modules on both sides of the unit, supporting up to eight modules per side for a maximum of sixteen modules from a single supply. For maintenance teams facing an aging or failed supply, this module is a direct replacement path that restores the architecture without a full controller overhaul.
What the 1769-PA4 Delivers to Your Panel
This is an open-style AC power supply module from the CompactLogix product line. It accepts a switch-selectable input voltage range of 85 to 265V AC or 170 to 265V AC, with a nominal input of 120/220V AC and an input frequency range of 47 to 63 Hz. On the output side, it provides 4.0 A at 5V DC and 2.0 A at 24V DC. Power consumption reaches 200 VA at 120V AC and 240 VA at 240V AC. Maximum inrush current is 25 A at 132V AC, and the continuous isolation voltage is 265V from AC input to the system.
Key Parameters That Drive Sizing Decisions
Current Capacity and Module Budget
The 4.0 A at 5V DC and 2.0 A at 24V DC outputs set the ceiling for how many I/O modules you can hang on the backplane. Before adding analog or high-density discrete modules, calculate the total load against these figures. Exceeding them causes intermittent faults that are hard to trace.
Power Supply Distance Rating
The distance rating of 8 means no module may sit more than eight positions from the power supply. With modules allowed on both sides, you reach the sixteen-module maximum. Ignoring this rule produces a configuration the controller will not accept.
Fuse Protection and Replacement
An internal fuse protects the supply. Replace it only with a Littelfuse 02153.15MXP or Wickmann 19195-3.15A fuse. Using an unmatched fuse risks damage and voids the protection design.
Physical Footprint
The unit measures approximately 118 x 70 x 87 mm (4.65 x 2.76 x 3.43 in.) and weighs 525 g (1.16 lb). It supports DIN rail or panel mounting, so it fits both new builds and retrofit cabinets.
Where This Supply Earns Its Keep
Discrete Output Heavy Assemblies
Panels running many discrete output modules draw heavily on the 5V DC rail. The 4.0 A capacity keeps those outputs switching without brownout symptoms.
Analog and Mixed I/O Racks
Analog modules are sensitive to unstable backplane voltage. The 1769-PA4 holds a steady rail, which protects measurement accuracy in process applications.
Legacy Line Replacement
When a supply fails on an existing CompactLogix line, matching the original catalog number avoids rewiring. This is the fastest route back to production.
Installation and Setup Essentials
Before energizing the unit, confirm the voltage selector switch matches your actual supply. The wrong setting can damage the module immediately. Use 14 AWG (2.5 mm2) solid copper wire rated at 90 °C (194 °F) or greater with 1.2 mm (3/64 in.) maximum insulation. Solid wire sizes from 22 to 14 AWG and stranded wire sizes from 22 to 16 AWG are accepted. Mount the unit on DIN rail or panel, then verify the bus lever is locked before applying power.
Reliability and Maintenance Planning
Inspect the supply periodically for loose terminal connections and heat discoloration. The open-style enclosure means the panel environment matters. Keep the cabinet within the operating range of 0 to 60 °C (32 to 140 °F) and maintain 5 to 95% relative humidity, non-condensing. The unit withstands 30 g shock and 5 g vibration at 10 to 500 Hz. Power dissipation is 8 W at 60 °C (140 °F), so allow airflow around the module. For ROI, a spare on the shelf costs far less than an hour of unplanned downtime.
Before You Order
Verify your existing catalog number, input voltage selection, and total module count against the distance rating. Confirm the fuse type available in your maintenance stock. Please verify current lifecycle status and availability with SpareTechPLC before ordering, and ask about companion CompactLogix components for a complete replacement kit.
Frequently Asked Questions
Can I mount the 1769-PA4 on a panel instead of DIN rail?
Yes. The unit supports both DIN rail and panel mounting, giving flexibility in retrofit cabinets.
How many I/O modules can one supply support?
Up to eight modules on each side, for a maximum of sixteen modules total.
Which fuse should I stock as a spare?
Use a Littelfuse 02153.15MXP or Wickmann 19195-3.15A replacement fuse only.
What wire gauge works with the terminal block?
Solid wire from 22 to 14 AWG and stranded wire from 22 to 16 AWG are accepted.
