WhatsApp: +86 16626708626
Email: 
Phone: +86 16626708626Description
Key Technical Specifications
- Catalog Number: 1746-IA8
- Manufacturer: Allen-Bradley
- Product Family: SLC 500
- Module Type: Digital AC input module
- Input Count: 8
- Input Voltage Range: 85-132 V AC
- Nominal Input Voltage: 100/120 V AC
- Input Frequency: 47-63 Hz
- Backplane Current at 5 VDC: 50 mA
- Signal ON Delay: 35 ms max
- Signal OFF Delay: 45 ms max
- Isolation: 1,500 V AC backplane to field side
Product Introduction
The Allen-Bradley 1746-IA8 is an 8-point AC input module for the SLC 500 platform. It reads 100/120 V AC field signals from switches, relays, and other discrete devices and reports them to the SLC backplane.
This module is a common legacy replacement part in older SLC 500 panels. The 1746-IA8 is chosen when you need the exact 8-point AC input format, 85-132 V AC range, and SLC 500 mechanical fit without changing the existing rack design.
Troubleshooting Quick Reference
| Symptom | Possible Cause | Relevance to this Part | Quick Check Method | Recommendation |
|---|---|---|---|---|
| Input LED never turns on | Missing field AC voltage | ✅ High | Measure 85-132 V AC at the input terminal with a meter | Check field wiring, fuse, and upstream device first |
| Input LED on, PLC bit stays off | Backplane or addressing issue | ⚠️ Medium | Verify the slot mapping in the processor program | Confirm the module is in the correct rack and slot |
| One channel stuck ON | External contact welded or leaking field voltage | ✅ High | Remove the field wire and recheck the input status | Inspect the external device before replacing the module |
| Several inputs read erratically | Shared neutral issue or noisy AC wiring | ✅ High | Check neutral continuity and measure line stability | Clean up wiring and grounding before condemning the card |
| All inputs dead after replacement | Wrong module type or no backplane power | ✅ High | Confirm the part number and measure rack power | Verify the 1746-IA8 and the chassis PSU |
| Slow response on input change | Normal module timing or PLC scan delay | ⚠️ Medium | Compare delay against the module specs and PLC scan time | Do not treat normal delay as a module failure |
If you are stuck, send photos of the wiring, slot location, and processor diagnostics to technical support.
1746-IA8
1746-IA8
Frequently Asked Questions
Q: What does the 1746-IA8 do?
It is an 8-point AC input module for the SLC 500 PLC family. It takes 100/120 V AC field signals and converts them into discrete input data for the controller.
Q: Is this module still in production?
No. Rockwell lists 1746 SLC I/O modules as discontinued, so most available stock is surplus or refurbished.
Q: Can I use 24 V DC on this input card?
No. This is an AC input module. If you put 24 V DC on it, it will not behave the way you expect.
Q: Is it plug-and-play with my SLC 500 rack?
Usually yes, if the rack, slot, and processor configuration match. Still, verify the exact catalog number and program addressing before you swap it in.
Q: What usually gets mistaken for a bad 1746-IA8?
Bad field wiring, blown fuses, bad contacts, shared neutral problems, or a slot mapping issue in the PLC program. The module itself is not always the culprit.
Q: What condition should I expect when buying one?
Most sellers offer New Surplus or Refurbished units. Ask for test status, photos, and warranty terms so you know what you are actually getting.
Q: What should I verify before ordering a replacement?
Check the voltage range, the input count, the chassis slot, and the exact series of the replacement. If the site uses 100/120 V AC signals, the 1746-IA8 is the right class of part, but the wiring still needs to be checked carefully.
