Description
Product Introduction
The Allen-Bradley 1769-PA4 is a high-output AC expansion power supply module designed for CompactLogix 1769 control systems and MicroLogix 1500 architectures. It provides regulated 5.1VDC and 24VDC logic power directly across the 1769 backplane, enabling reliable system boot and continuous module operation.
Engineered for higher density systems, the 1769-PA4 delivers double the 5VDC backplane current capacity of the standard 1769-PA2 supply (4.0 A vs 2.0 A). It can be mounted locally on the main CPU bank or positioned on secondary expansion banks connected via 1769 bus cables, ensuring stable power delivery across complex, multi-bank I/O layouts.
Key Technical Specifications
| Parameter | Value |
| Input Voltage Range | 85 to 265 VAC (Selectable/Auto-Ranging 120V/240V AC Nominal) |
| Line Frequency Range | 47 to 63 Hz |
| Power Consumption | 200 VA @ 120VAC | 240 VA @ 240VAC |
| Backplane Current @ 5.1VDC | 4.0 A Max |
| Backplane Current @ 24VDC | 2.0 A Max |
| Inrush Current | 30 A Max @ 132VAC for 10 ms |
| Fuse Type | Littelfuse 0216008.MXP (8 A, 250V Slow-Blow) or equivalent |
| Power Distance Rating | Mounts within power distance limits of adjacent I/O modules |
| Operating Temperature | 0°C to 60°C (32°F to 140°F) |
| Wiring Connection | Finger-Safe Screw Terminal Block (12 to 22 AWG wire) |
- 1769-PA4
- 1769-PA4
- 1769-PA4
Application Scenarios & The “Trench” Experience
The Trench Story
It is 4:00 AM on a critical automotive line startup. An expanding CompactLogix rack populated with high-density output modules (like multiple 1769-OB32 cards) keeps suffering random backplane brownout faults during heavy output energization cycles. The existing power supply (1769-PA2) was running at its absolute limit, dropping 5VDC logic levels every time all solenoids fired simultaneously. Swapping the undersized supply for a 1769-PA4 doubles the available 5VDC backplane current headroom from 2.0 A to 4.0 A. Logic power stabilizes instantly, clearing intermittent CPU backplane faults and allowing line commissioning to finish on schedule.
Specific Applications
- High-Density I/O Banks: Supplies continuous logic power to racks loaded with 32-point digital modules and analog cards requiring high backplane current.
- Secondary Expansion Racks: Powers second and third 1769 expansion banks connected via 1769-CRI or 1769-CRR expansion bus cables.
- Legacy MicroLogix 1500 Systems: Provides reliable 120/240VAC panel power to expanded MicroLogix 1500 controller installations.
- Process Machinery Skids: Serves as the primary system power hub in industrial panels where only 120VAC or 230VAC utility power is routed.
Transparency SOP: Quality Assurance & Testing
Every 1769-PA4 power supply module undergoes a multi-point electrical load test before joining our active inventory:
- Mechanical & Terminal Inspection: We check side locking latches, clean backplane bus contacts, and verify that terminal block screws and the protective flip-door are in good condition.
- AC Line Surge & Universal Input Test: The unit is powered across full voltage swings (85VAC up to 265VAC at 50Hz and 60Hz) to confirm internal transformer and rectifier stability.
- Dual Rail Load-Bank Burn-In: We connect a full electronic load to both backplane rails simultaneously (pulling a full 4.0 A load on 5.1VDC and 2.0 A on 24VDC) for two hours to verify thermal performance.
- Ripple & Noise Measurement: Output rails are monitored on an oscilloscope under load to confirm ripple voltage remains within strict Rockwell specifications.
- Fuse & Protection Verification: We inspect internal slow-blow fuse integrity and verify short-circuit shutdown and auto-recovery functionality.
The Veteran’s Tech Trap Guide
- ⚠️ Calculate Your Backplane Power Budget First: Adding modules to a 1769 bank without verifying current draw can overload even a 1769-PA4. Calculate the total 5.1VDC and 24VDC current draw of every module on the bank using Integrated Architecture Builder (IAB) or manual spec tallying to ensure total draw remains under 4.0 A @ 5.1V and 2.0 A @ 24V.
- ❗ Mind the Power Distance Rating of Surrounding Modules: The 1769-PA4 supplies power to modules on both its left and right sides, but each adjacent I/O card has a specific “Power Distance Rating” (e.g., 4, 5, or 6 slots). No module can be placed further from the 1769-PA4 than its rated slot distance limit, or it will suffer voltage drop issues.
- ⚠️ Do Not Confuse 1769-PA4 (AC) with 1769-PB4 (DC): The 1769-PA4 requires an AC line input (120/240VAC). Wiring 24VDC panel power to the 1769-PA4 terminal block will result in a completely dead unit. If your control panel runs strictly on 24VDC power, you MUST use the 1769-PB4 power supply instead.
- ❗ Check the Blown Fuse Indicator LED: If the module status LED is completely OFF despite AC input power being applied, check the internal 8 A slow-blow fuse located behind the front protective cover before assuming total component failure.
Frequently Asked Questions
Q: What is the main difference between the 1769-PA2 and the 1769-PA4?
The primary difference is current output capacity. The 1769-PA4 provides 4.0 A @ 5.1VDC and 2.0 A @ 24VDC, whereas the smaller 1769-PA2 only provides 2.0 A @ 5.1VDC and 0.8 A @ 24VDC. Both accept 120/240VAC inputs.
Q: Can I install two 1769-PA4 power supplies in the exact same local I/O bank?
No. You cannot install two power supplies in parallel on a single 1769 backplane bank to increase current. If a single bank exceeds the capacity of one 1769-PA4, you must split the modules into a secondary expansion bank connected via a 1769 expansion cable and power that second bank with its own dedicated power supply.
Q: Does the 1769-PA4 supply 24VDC field power for field sensors and solenoid outputs?
No. The 24VDC provided by the 1769-PA4 is strictly backplane logic power for operating internal module circuitry. Field devices (like output solenoids or 4–20mA loops) require separate, dedicated external 24VDC field power wired to the individual I/O module terminal blocks.
Q: Is the 1769-PA4 compatible with all CompactLogix 5370 L3 controllers?
Yes. The 1769-PA4 is fully compatible with CompactLogix L3 processors (such as 1769-L32E, 1769-L33ER, and 1769-L35ER) as well as legacy MicroLogix 1500 controllers.
Q: What replacement fuse does the 1769-PA4 use?
It uses a standard 5 \times 20 mm, 8 A, 250V slow-blow ceramic fuse (Littelfuse part number 0216008.MXP or equivalent).
Q: What warranty is included with your surplus and refurbished 1769-PA4 units?
Every 1769-PA4 module we ship includes our full 12-month replacement warranty. If a power delivery fault or hardware failure occurs under normal operating conditions within 365 days of purchase, we replace the unit immediately from stock or issue a full refund.
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