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Key Technical Specifications
| Parameter | Value |
|---|---|
| Catalog Number | 1786-RPA (also listed as 1786-RPA/B) |
| Module Type | ControlNet Modular Repeater Adapter |
| Network Protocol | ControlNet (IEC 61158 / ODVA) |
| Coax Port | 1 × RG6 copper coax, BNC connector |
| Input Voltage | 24 V DC nominal (18–36 V DC range) |
| Input Current | 700 mA @ 24 V DC max (Class 2 / SELV) |
| Power Consumption | 16.8 W max |
| Power Dissipation | 8.8 W max |
| Backplane Output | 1.6 A @ 5 V DC max |
| Supported Topologies | Linear, star, ring, point-to-point |
| Max Adapters in Series | 20 × 1786-RPA modules |
| Mounting | DIN rail or panel mount |
| Enclosure Rating | IP20 |
| Operating Temperature | 0 to 60 °C (32 to 140 °F) |
| Storage Temperature | −40 to 85 °C (−40 to 185 °F) |
| Humidity | 5–95% non-condensing |
| Dimensions (H × W × D) | ~12 × 7.75 × 4 in (304.8 × 196.8 × 101.6 mm) |
| Wire Size (Power) | 24–12 AWG (0.21–3.3 mm²) solid or stranded copper, 105 °C rated |
| Certifications | UL, CE, CSA; Ex nA IIC T5 Gc (EN 60079-15) |
Product Introduction
The Allen-Bradley 1786-RPA is a ControlNet modular repeater adapter used to extend and regenerate ControlNet coax segments in legacy ControlLogix, CompactLogix, FlexLogix, and SLC 500 systems. It provides one RG6 coax BNC port and converts 24 V DC input to a 5 V DC backplane supply for mounting additional 1786 repeater modules (e.g., 1786-RPFRL, 1786-RPFRXL).
This module is chosen for building multi-segment ControlNet networks where signal regeneration and electrical isolation are needed. In field deployments, it’s commonly used in oil & gas, power generation, water treatment, and metals processing where ControlNet remains the backbone network.
1786-RPA
1786-RPA
Troubleshooting Quick Reference
| Symptom | Possible Cause | Relevance to this Part | Quick Check Method | Recommendation |
|---|---|---|---|---|
| No power LED on module | 24 V DC supply missing or wiring fault | ✅ High | Measure 24 V DC at input terminals; check polarity and fuse | Fix 24 V DC supply and wiring before swapping module |
| Network LED off or flashing red | Coax segment fault or termination issue | ✅ High | Check coax continuity; verify 75 Ω terminators at both ends | Replace damaged coax; ensure proper termination |
| Intermittent ControlNet comms | Poor connections or EMI | ✅ Medium | Inspect BNC connectors; check cable routing near VFDs/motors | Re-terminate coax; improve shielding and grounding |
| Backplane modules not powering | 5 V DC backplane output fault | ✅ High | Measure 5 V DC at backplane terminals; check load current | Reduce backplane load; replace module if 5 V is out of spec |
| Excessive heat from module | Overload or poor ventilation | ✅ Medium | Measure input current; check enclosure temperature | Improve airflow; verify input voltage within 18–36 V DC |
| Network faults after adding repeater | Too many repeaters in series or config error | ❌ Medium | Count repeaters in series (max 20); verify network config | Reduce repeater count; verify ControlNet schedule and NUT |
If you’re stuck, send photos of the module (including LEDs), a network diagram, and a list of connected devices. We’ll review it before you swap the module.
Frequently Asked Questions (FAQ)
Q: Is the 1786-RPA hot-swappable?
A: No. The 1786-RPA must be installed and removed with 24 V DC power OFF. Hot-swapping can damage the backplane and connected repeater modules.
Q: What’s the difference between 1786-RPA and 1786-RPCD?
A: RPA is a modular repeater adapter with 24 V DC input and 5 V DC backplane output for mounting fiber or coax repeater modules. RPCD is a ControlNet repeater with integrated power and coax ports. RPA is used to build custom repeater configurations.
Q: How many 1786-RPA modules can I connect in series?
A: Maximum 20 × 1786-RPA modules in series. Exceeding this limit can cause signal degradation and network faults.
Q: Can I use the 1786-RPA with fiber optic repeaters?
A: Yes. The 1786-RPA backplane supports 1786 fiber repeater modules (e.g., 1786-RPFRL, 1786-RPFRXL). Ensure total backplane current does not exceed 1.6 A.
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, and Rockwell has discontinued the 1786-RPA as of Dec 31, 2025. Each refurbished unit goes through live functional testing and comes with a 1-year warranty.
Q: Do I need to configure the 1786-RPA in RSLogix?
A: No. The 1786-RPA is a passive repeater adapter. It does not require configuration in RSLogix or ControlNet scheduling. However, connected repeater modules may need to be accounted for in network planning.
Q: What power supply do I need for the 1786-RPA?
A: Use a 24 V DC, Class 2 / SELV power supply capable of at least 700 mA. For multiple repeaters, size the supply for total current (700 mA × number of RPAs plus backplane load).
