Power Supply Module | Allen-Bradley 1771-P6S1 PLC-5

The 1771-P6S1 is a single-slot modular AC power supply manufactured by Allen-Bradley for the PLC-5 and 1771 Universal I/O platform. Designed to plug directly into any standard slot of a 1771 I/O chassis, it converts nominal 200/220 V AC input power into a regulated 8 A output at 5 V DC, delivering low-voltage logic power straight to the chassis backplane. This slot-mount design eliminates external panel space requirements and allows system builders to configure single, parallel, or redundant power architectures within the same I/O rack.

Electrical Output and Redundancy Architecture

Operating at an input rating of 200/220 V AC (170–240 V AC nominal range) across 47 to 63 Hz, the module supplies up to 8 A of current to power installed PLC-5 processors, remote I/O adapters, and I/O modules. For systems with higher current requirements or critical availability demands, multiple 1771-P6S1 units can be installed in parallel using interconnecting cables to supply up to 16 A per chassis or configured for seamless N+1 power redundancy.

Installation and Hardware Configuration

The module features rear-mounted configuration jumpers that select between local and remote sensing to maintain precise output voltage regulation across backplane connections. Front-panel status indication is provided by a P/S ACTIVE LED, which signals normal DC output status and alerts maintenance staff during undervoltage or overvoltage shutdown conditions. Wiring connections for AC power line, ground, and alarm status are made via a removable 5-position front terminal block.

Troubleshooting and System Diagnostics

When diagnosing power issues on a 1771-P6S1 module, follow these essential operational verification steps:

1. Verify Line Power & Input Voltage: Measure incoming AC power across the terminal block. Ensure line voltage sits within the specified 170–240 V AC operating band.
2. Check P/S Active Status: Inspect the front-panel P/S ACTIVE indicator. Verification: A steady illuminated green status LED confirms normal output voltage regulation to the backplane.
3. Handle Overvoltage or Current Fault Shutdowns: If the P/S ACTIVE LED turns off due to backplane overcurrent or voltage limit trips, disconnect AC mains power for a minimum of 5 seconds to reset internal latching protection circuits before re-energizing.

Frequently Asked Questions

Q: What is the main difference between a standalone supply like the 1771-PA and the 1771-P6S1? A: The 1771-P6S1 is an internal single-slot module that plugs directly into an I/O slot on the backplane, whereas the 1771-PA is an external standalone power supply mounted beside or above the chassis.

Q: Can multiple 1771-P6S1 modules be installed in the same 1771 I/O chassis? A: Yes, multiple 1771-P6S1 modules can be installed in parallel using paralleling cables to increase available backplane current up to 16 A or to provide redundant power supply backup.