Allen-Bradley 1746-A4 — 4-Slot Modular Backplane Chassis | SLC 500 Platform
Engineering Background
The Allen-Bradley 1746-A4 is a 4-slot modular chassis designed for the SLC 500 programmable controller family — one of Rockwell Automation’s most widely deployed small-to-mid-range PLC platforms in global industrial automation. Introduced as part of the 1746 hardware series, the chassis serves as the structural and electrical backbone that integrates the power supply, processor, and I/O modules into a unified control node.
Product Positioning
The 1746-A4 is the entry-level chassis in the SLC 500 modular lineup, offering 4 I/O module slots (excluding the processor slot). It is optimally suited for compact control applications where panel space is constrained but full SLC 500 processor capability is required. Procurement engineers specifying retrofit, spare, or new-build SLC 500 systems will find the 1746-A4 the most cost-effective chassis entry point within the 1746 series.
Complete Technical Specifications
- Catalog Number: 1746-A4
- Platform: Allen-Bradley SLC 500 (1746 Series)
- Chassis Slots: 4 I/O module slots (1 processor slot + 4 I/O slots total)
- Backplane Bus: SLC 500 parallel backplane
- Compatible Processors: SLC 5/01, 5/02, 5/03, 5/04, 5/05 (1747-Lxxx series)
- Compatible Power Supplies: 1746-P1, 1746-P2, 1746-P3, 1746-P4, 1746-P7
- Module Compatibility: All 1746 series digital, analog, specialty, and communication I/O modules
- Mounting: DIN rail or panel mount
- Weight: 1,550 g (approx.)
- Manufacturer: Rockwell Automation / Allen-Bradley
- Country of Origin: USA
- Certification: UL, CE, CSA (per Rockwell Automation product certification)
Proven Application Environments
- Discrete manufacturing lines (automotive, electronics assembly, packaging)
- Process control panels in food & beverage and pharmaceutical facilities
- Water/wastewater treatment SCADA nodes
- OEM machine builders requiring compact SLC 500 control architecture
- MRO (Maintenance, Repair & Operations) spare chassis for existing SLC 500 installations
- Retrofit and modernization projects where SLC 500 compatibility must be preserved
Engineering Advantages
- Compact Footprint: 4-slot form factor minimizes panel real estate while retaining full SLC 500 processor capability.
- Modular Expandability: Supports chassis interconnect via 1746-A7, 1746-A10, or 1746-A13 expansion chassis when I/O count grows.
- Broad I/O Compatibility: Accepts the full range of 1746 series I/O modules — digital, analog, thermocouple, RTD, high-speed counter, and communication adapters.
- Proven Reliability: SLC 500 platform has a multi-decade field track record in harsh industrial environments.
- Standardized Spare Parts: Widely stocked globally, reducing lead time risk for MRO procurement.
System Architecture & Signal Flow
In a standard SLC 500 modular system, the 1746-A4 chassis houses the following in left-to-right slot order:
- Slot 0: SLC 500 Processor (1747-Lxxx) — program execution, I/O scan, communication
- Slots 1–4: 1746 series I/O modules — digital inputs/outputs, analog I/O, or specialty modules
- Power Supply: Mounted to the left of the chassis (1746-Pxxx), feeds regulated DC backplane power to all slots
The backplane provides both power distribution and the parallel data bus for processor-to-I/O communication. All module addressing is slot-based, configured via RSLogix 500 / Studio 5000 Logix Designer (legacy compatibility mode).
Sourcing & Quality Verification
- All units sourced through verified industrial automation supply channels.
- Each unit inspected for physical integrity, backplane connector condition, and label authenticity prior to dispatch.
- Catalog number, date code, and series markings verified against Rockwell Automation documentation.
- New surplus, refurbished, and used-tested grades available — condition specified at time of quotation.
- Traceability documentation available upon request for critical infrastructure procurement.
Procurement Process
- Step 1: Confirm required chassis slot count and compatible processor/power supply catalog numbers.
- Step 2: Submit RFQ via support@konmask.com or place order directly on Konmask.com.
- Step 3: Receive quotation with lead time, condition grade, and shipping options within 1 business day.
- Step 4: Order confirmation, quality inspection, and dispatch with tracking.
- Step 5: Post-delivery technical support available for installation and commissioning queries.
Technical FAQ
- Q: How many I/O modules can the 1746-A4 accommodate?
- A: 4 I/O module slots. Slot 0 is reserved for the SLC 500 processor; slots 1–4 accept any 1746 series I/O or communication module.
- Q: Can the 1746-A4 be expanded with additional chassis?
- A: Yes. Using a 1746-A2 or 1746-BAS adapter, up to 3 expansion chassis (1746-A7, A10, or A13) can be connected, supporting up to 30 total I/O slots per system.
- Q: Which power supplies are compatible?
- A: 1746-P1 (120V AC), 1746-P2 (120/240V AC), 1746-P3 (24V DC), 1746-P4 (120/240V AC high-capacity), and 1746-P7 (24V DC high-capacity).
- Q: Is the SLC 500 platform still supported by Rockwell Automation?
- A: The SLC 500 is in End of Life status. Rockwell Automation recommends migration to the CompactLogix (1769) platform. However, spare parts and MRO supply remain widely available through authorized and independent distributors.
- Q: What programming software is used with SLC 500?
- A: RSLogix 500 is the native programming environment. Studio 5000 Logix Designer also supports SLC 500 in legacy compatibility mode.
- Q: Do you provide a warranty?
- A: Yes. Warranty terms are provided at time of quotation based on unit condition grade. Contact support@konmask.com for details.
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