Allen‑Bradley 1771‑A4B I/O Chassis Inquiry Item

This Allen‑Bradley 1771‑A4B is a 16-slot universal I/O chassis for Rockwell PLC‑5 control system. It provides backplane bus and 5.25VDC power distribution for all inserted 1771 series modules, including processor, remote I/O adapter, digital and analog I/O modules. It supports half-slot addressing mode, can be used as local rack or remote I/O rack matched with 1771‑ASB adapter. This product has been discontinued for many years, only used for maintenance replacement of old production lines, water treatment, metallurgy and chemical legacy PLC‑5 control cabinets.

Specifications

Model: 1771‑A4B Brand: Allen‑Bradley (Rockwell) Series: PLC‑5 / 1771 Slot quantity: 16 slots Backplane voltage: 5.25VDC Backplane current rating: 24A Addressing: Half-slot addressing Installation: Panel rear mounting Certifications: CE, UL, CSA Protection class: IP20

Components & Troubleshooting

Backplane PCB board, metal frame, module guide rail, bus gold finger connector, grounding terminal. Common faults: Backplane bus contact poor, slot no communication, backplane short circuit causing power trip, bus corrosion, slot pin oxidation.

Disclaimer

This spare part shall be installed, calibrated and maintained by qualified instrument technicians. Power off the rack before plugging and unplugging modules.