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Phone: +86 16626708626Description
Key Technical Specifications
| Parameter | Value |
|---|---|
| Catalog Number | 1771-PA (also listed as 1771-PA/B) |
| Module Type | Power Supply for 1771 I/O Chassis |
| Input Voltage (Nominal) | 120 / 220 V AC (selectable via jumper) |
| Input Voltage Range | 97–132 V AC or 195–264 V AC |
| Input Frequency | 47–63 Hz |
| Max Input Current | 1.0 A @ 120 V AC; 0.5 A @ 220 V AC |
| Max Real Input Power | 108 W |
| Max Apparent Input Power | 176 VA |
| Max Transformer Load | 270 VA |
| Backplane Output Voltage | 5 V DC (regulated) |
| Backplane Output Current | 16 A continuous @ 5 V DC |
| Backplane Regulation | ±5% (typical) |
| Chassis Compatibility | 1771-A1, A2, A4, A10, A13, B-series chassis |
| Slot Width | Single slot (leftmost slot in 1771 chassis) |
| Operating Temperature | 0 to 60 °C (32 to 140 °F) |
| Humidity | 5–95% non-condensing |
| Mounting Orientation | Vertical; minimum clearance above/below for cooling |
| Fuse | 3 A, 250 V, normal-blow (user-replaceable) |
| Dimensions | ~4.5 × 12.4 × 6.3 in (115 × 317 × 160 mm) |
| Weight | ~11.5 lb (5.2 kg) |
| Certifications | UL, CE, CSA (industrial use) |
Product Introduction
The Allen-Bradley 1771-PA is a single-slot power supply module for 1771 I/O chassis used with PLC-5 and legacy PLC-2 systems. It converts 120/220 V AC line power to a regulated 5 V DC @ 16 A backplane supply to run processors, adapters, and I/O modules in a 1771 rack.
This unit is chosen for its high backplane current capacity (16 A), selectable input voltage, and proven reliability in legacy panels. In field deployments, it’s the standard choice for medium to large 1771 chassis where multiple analog and digital modules must be powered from a single supply.
1771-PA
1771-PA
1771-PA
Troubleshooting Quick Reference
| Symptom | Possible Cause | Relevance to this Part | Quick Check Method | Recommendation |
|---|---|---|---|---|
| No LEDs, chassis dead | AC input missing or fuse blown | ✅ High | Measure AC at input terminals; check 3 A fuse continuity | Replace fuse if open; verify input voltage and wiring |
| RUN LED on, but modules reset intermittently | Overload or brownout on backplane | ✅ High | Measure 5 V DC at backplane under load; check total module current draw | Reduce load or add second supply; verify 16 A limit not exceeded |
| Chassis powers up then shuts down | Thermal shutdown or overcurrent | ✅ High | Check airflow and mounting orientation; measure backplane current | Improve cooling; verify no shorted modules on backplane |
| 5 V DC out of range (>5.25 V or <4.75 V) | Aging supply or poor regulation | ✅ Medium | Measure 5 V DC at multiple points on backplane | Replace supply if regulation is out of spec |
| Only some modules work | Backplane slot damage or wiring issue | ❌ Medium | Test known-good module in multiple slots | Repair/replace chassis if specific slots fail |
| Input voltage selector mis-set | Jumper set wrong for site voltage | ✅ High | Visually inspect 120/220 V selector jumper | Set jumper to match site voltage before applying power |
If you’re stuck, send photos of the module (including jumper setting), a voltage reading at the backplane, and a list of installed modules. We’ll help you decide if it’s the supply or a downstream issue.
Frequently Asked Questions (FAQ)
Q: Is the 1771-PA hot-swappable?
A: No. The 1771 power supply must be installed and removed with AC power OFF. Hot-swapping can damage the backplane and other modules.
Q: Can I use the 1771-PA with PLC-5 controllers?
A: Yes. The 1771-PA is commonly used with PLC-5 systems in 1771 chassis. Some older references mention PLC-2, but it is widely deployed with PLC-5 as the standard 1771 power supply.
Q: What’s the difference between 1771-PA and 1771-P7?
A: PA is 120/220 V AC input with 5 V DC @ 16 A output. P7 is a higher-capacity supply (often 24 A or more, depending on variant) for larger chassis. Check your chassis size and total module current draw before choosing.
Q: How do I set the input voltage on the 1771-PA?
A: There is a voltage selector jumper on the module for 120 V or 220 V AC. Set it to match your site voltage before applying power. Installing with the wrong setting can damage the supply.
Q: What condition are these modules in, and why is pricing lower than factory?
A: We sell New Original (New Surplus) and Refurbished (tested) units. Pricing is lower because these are surplus or professionally refurbished, not current factory production. Each refurbished unit goes through load testing and comes with a 1-year warranty.
Q: Can I keep my existing program when swapping a failed 1771-PA?
A: Yes. The power supply is hardware only; it does not affect your PLC program. As long as the replacement is the same catalog number (1771-PA) and input voltage is set correctly, the system should power up normally.
Q: Do I need a special wiring arm for the 1771-PA?
A: No. The 1771-PA uses direct terminal connections for AC input and does not use a standard I/O wiring arm like digital or analog modules. Follow the OEM wiring diagram for line, neutral, and ground.
