Allen-Bradley 1746-NO8I SLC 500 8-Channel Analog Current Output Module

Description

Key Technical Specifications

Product Introduction & Supply Chain Strategy

The Allen-Bradley 1746-NO8I is an 8-channel high-density analog current output module engineered for the SLC 500 PLC platform. It translates 16-bit digital register data from the central processor into precise 0 to 20 mA or 4 to 20 mA analog signals to command variable frequency drives (VFDs), control valves, chart recorders, and positioners.

Because Rockwell Automation has retired the legacy SLC 500 product family, stocking uncommissioned New Surplus 1746-NO8I modules is an essential strategy for protecting complex process loops from unplanned downtime. Sourcing genuine New Surplus stock eliminates output ripple, calibration shift, and loop driver failure risks commonly found in second-hand pull-outs.

Installation & Configuration Guide

Stage 1: Pre-Installation (Prep & Safety)

1. Execute Lock-Out/Tag-Out (LOTO) on the main 1746 chassis power supply and external 24V DC loop power supplies.
2. Put on an ESD-grounded wrist strap connected to cabinet earth ground.
3. Document terminal wiring assignments and external power routing using reference photos before removing existing field connections.

Stage 2: Removal

1. Unfasten the retaining screws on the removable terminal block (RTB) and carefully detach it from the module front header.
2. Depress the upper and lower module release latches on the SLC 500 chassis frame simultaneously.
3. Slide the card straight out of the slot along its guide rails to prevent twisting or damaging backplane edge connector pins.

Stage 3: Installation (Clone & Seat)

1. Verify DIP switch or jumper configurations on the replacement 1746-NO8I card (such as backplane class settings or output behavior on fault) match the original module.
2. Align the circuit board edges with the top and bottom guides of the designated chassis slot.
3. Push the module firmly into the slot until both upper and lower latches snap into place securely.
4. Align the pre-wired RTB onto the terminal header and tighten the retaining screws to 0.5 N·m (4.4 lb·in).

Stage 4: Power-On & Testing

1. Re-apply external 24V DC loop power and confirm proper polarity across field current loop connections.
2. Apply power to the 1746 chassis power supply and observe the front status LEDs:
   • MODULE STATUS: Solid green indicates successful POST diagnostic execution.
   • CHANNEL STATUS (0–7): Green indicates normal channel operation; flashing red indicates an open loop condition or missing field power.
3. Online via RSLogix 500, access the output data register table (O:e.0 through O:e.7, where e is the slot number), force test values (e.g., 4 mA, 12 mA, 20 mA), and verify actual loop current with a calibrated multimeter.

1746-NO8I

1746-NO8I

Firmware/Software Versions & Upgrade Notes

• Class Addressing: The 1746-NO8I can operate in Class 1 or Class 3 mode based on software configuration and rack position. Ensure the slot configuration in RSLogix 500 matches the exact hardware series (Series A or Series B) to prevent backplane communication errors.
• Fault Handling Configuration: Configurable write words define module behavior (Hold Last State vs. Reset to 0 mA) during CPU fault or program mode conditions. Verify ladder logic properly initializes configuration words on system boot.
• Firmware Notes: Analog output cards utilize factory-calibrated D/A hardware logic and do not support field firmware flashes. Hardware replacement is plug-and-play provided software configuration matches existing program files.

Frequently Asked Questions (FAQ)

Q: Is this 1746-NO8I module a Brand New Surplus unit or a refurbished part?

A: This product is a Brand New Surplus unit. It is not used, not pulled from a decommissioned plant, and not refurbished. All modules undergo rigorous quality verification to ensure OEM-level reliability.

Q: Why is buying New Surplus preferable to a cheaper refurbished 1746-NO8I card?

A: Analog output modules rely on precision onboard digital-to-analog converters, voltage references, and linear current drivers. Refurbished boards often suffer from thermal degradation, output current drift, or failed optical isolation channels due to years of industrial field service. Investing in New Surplus guarantees factory-level accuracy, a 10 to 15-year operational lifespan, and zero risk of unexpected valve or drive command failures.

Q: How do you verify the quality and authenticity of legacy Allen-Bradley modules?

A: Every unit undergoes our inbound SOP quality verification: inspecting original OEM ESD packaging, verifying zero backplane pin insertion wear, confirming hardware revision consistency, and performing live loop power and output current signal verification on an SLC 500 test chassis.

Q: Does the 1746- require an external 24V DC power supply for output loops?

A: Yes. The 1746- requires an external 24V DC loop power supply connected across the field wiring terminals to drive current through output loads up to 500 \Omega.

Q: Is it safe to hot-swap the 1746- while the SLC 500 rack is powered up?

A: No. Allen-Bradley SLC 500 chassis backplanes do not support Hot-Swapping (RIUP). Removing or inserting any 1746 card while backplane power is active causes arcing that can destroy the module, adjacent I/O cards, or the primary CPU. Always disconnect chassis power first.

Q: What warranty coverage applies to this New Surplus 1746-?

A: All 1746- New Surplus cards carry our comprehensive 1-year functional replacement warranty. If any channel or internal component fails under standard operating parameters, we will immediately supply a replacement card or issue a full refund.