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Key Technical Specifications
| Parameter | Value |
| Catalog Number | 1771-P7 |
| Input Voltage | 120 VAC (97–132 VAC) or 220/240 VAC (195–264 VAC), selectable |
| Input Frequency | 47–63 Hz |
| Real Power Consumption | 125 W maximum |
| Apparent Power Consumption | 210 VA maximum |
| Output Voltage | 5 VDC (regulated) |
| Output Current | 16 A maximum at 50°C (16,000 mA) |
| Inrush Current | 20 A peak for 1/2 cycle at 120 VAC |
| Location / Mounting | Mounts directly in the left-most slot of 1771 I/O chassis |
| Fuse Rating | 2.5 A, 250 V slow-blow (3AG) |
| Operating Temperature | 0 to 60°C (32 to 140°F) |
Product Introduction & Supply Chain Strategy
The Allen-Bradley 1771-P7 is a high-capacity chassis-mount power supply designed to deliver up to 16 A of regulated 5 VDC power directly across the 1771 backplane bus. Operating on either 120 VAC or 220/240 VAC input, it energizes the processors, communication adapters, and I/O module logic circuits installed within PLC-5 rack assemblies.
As Rockwell Automation has fully discontinued the legacy 1771 platform, power supplies represent the primary single-point-of-failure risk across installed systems. Choosing verified New Surplus units prevents severe operational disruptions caused by drying filter capacitors and transformer degradation common in aged, refurbished supplies. Sourcing pristine surplus stock secures 100% backplane stability while eliminating the substantial capital expenditure of immediate PLC platform migration.
Installation & Configuration Guide
Stage 1: Pre-Installation (Prep & Safety)
- Lock-Out/Tag-Out (LOTO): Disconnect and lock out all incoming AC mains power feeding the enclosure prior to mounting or wiring.
- Voltage Selection Verification: Ensure internal voltage selection jumpers or terminal connections are set correctly for your local line supply (120 VAC vs. 220/240 VAC).
- ESD Protection: Put on a grounded wrist strap to prevent static discharges to adjacent chassis backplane connections.
Stage 2: Removal
- De-energize the incoming AC line and disconnect field wiring from the front-facing terminal strip.
- Unscrew the upper and lower mounting retention screws securing the supply to the chassis frame.
- Carefully pull the power supply straight forward out of the left-most chassis slot to clear the backplane edge connector.
Stage 3: Installation (Clone & Seat)
- Verify that the 1771 chassis left slot card guides are free of debris and damage.
- Align the 1771-P7 module with the guide rails and slide it firmly into place until the rear power connector seats fully into the backplane.
- Tighten the top and bottom mounting screws to ensure proper grounding continuity with the chassis.
- Wire the incoming AC power conductors (Line, Neutral, Equipment Ground) securely to the front terminal strip.
Stage 4: Power-On & Testing
- Measure the input supply voltage with a digital multimeter to confirm line stability within operating limits (97–132 VAC or 195–264 VAC).
- Apply input power and confirm that the front panel green “DC ON” LED illuminates brightly.
- Check the 5 VDC backplane bus voltage at test points to verify it falls strictly within the acceptable 5.1 VDC ±0.1 VDC range before initiating CPU run modes.
1771-P7
1771-P7
1771-P7
Firmware/Software Versions & Upgrade Notes
- Hardware Architecture: The 1771-P7 is an analog/digital switching power supply and contains no flashable firmware or software interfaces.
- Chassis Compatibility: Directly compatible with standard 1771-A1B, 1771-A2B, 1771-A3B, and 1771-A4B I/O chassis assemblies.
- Power Budgeting: Calculate total backplane current consumption across all installed CPU, communication, and I/O cards prior to commissioning. Total continuous 5 VDC current load must not exceed 16 A; exceedances will trip internal over-current protection circuits and cause thermal shutdowns.
Frequently Asked Questions (FAQ)
Is this 1771-P7 unit guaranteed to be New Surplus rather than refurbished?
Yes. This module is 100% Brand New Surplus stock in factory-original condition. It has never been deployed in a plant panel, repaired, or rebuilt with third-party components. Internal capacitors, transformers, and backplane connectors show zero thermal degradation or physical wear.
Why shouldn’t I buy a cheaper refurbished 1771-P7 power supply?
Power supplies are thermal stress points in industrial control panels. Refurbished units frequently contain aged electrolytic capacitors that suffer from electrolyte drying and elevated Equivalent Series Resistance (ESR). This causes excessive 5 VDC voltage ripple, leading to unexplained CPU faults, corrupt I/O data, and unpredictable plant trips.
Can I use the 1771-P7 for parallel redundant power configurations?
No. The standard 1771-P7 power supply does not include internal isolation diodes required for direct parallel load sharing. For redundant power configurations, specialized 1771 redundant power supply systems (such as the 1771-P11 or 1771-PS7) and cabling harnesses must be utilized.
What should I do if the front “DC ON” LED remains unlit after applying power?
First, isolate incoming AC power and check the front-panel 2.5 A slow-blow fuse using a multimeter continuity check. If blown, inspect field terminal wiring for shorts. If the fuse is intact and incoming AC voltage is verified, replace the unit; an unlit LED under valid input indicates an internal over-voltage or over-current shutdown response.
What warranty protection is provided with this New Surplus unit?
We support this 1771-P7 New Surplus power supply with a comprehensive 1-year replacement warranty. Every unit undergoes complete visual inspection, insulation testing, and full-load power verification prior to ESD-safe packaging and shipment.
