1746-A10 — SLC 500 10-Slot Modular Chassis

The 1746-A10 is a 10-slot modular chassis for the SLC 500 control system. It provides the physical housing and backplane that connects the power supply, CPU module, and up to nine I/O modules. The chassis itself contains no electronics — it's the structural and electrical bus that all SLC 500 modules plug into. Without a matching chassis, SLC 500 modules can't be installed or operated.

The SLC 500 is a well-established, deeply-installed controller platform from the late 1980s through 2000s, with hundreds of thousands of systems still running in production environments worldwide. The 1746-A10 chassis is the backbone of many of those installations. Whether the need is a like-for-like replacement of a failed chassis, expansion of an existing system, or spare parts procurement for long-term maintenance, this is the 10-slot standard for SLC 500 modular builds.

Specifications

Parameter	Value
Part Number	1746-A10
Platform	SLC 500 (1746 series)
Total Slots	10 (Slot 0 = power supply, Slots 1–9 = CPU or I/O)
User I/O Slots	9 (Slot 1 for CPU; Slots 2–9 for additional I/O)
Backplane	SLC 500 parallel backplane (7.5V, 1A per slot typical)
Power Supply Slot	Slot 0 (left end, dedicated)
Module Compatibility	All 1746-series SLC 500 I/O and specialty modules
Mounting	DIN rail or panel surface (4 × M5 or #10-32 screws)
Enclosure	Open chassis (requires panel enclosure)
Operating Temperature	0°C to 60°C
Standards	UL 508, CE

Keeping an Aging SLC System Reliable

For facilities maintaining existing SLC 500 systems, a few practices significantly reduce unplanned downtime risk:

Chassis inspection: periodically inspect the backplane connectors in empty slots for corrosion or debris. Conductive contamination on the backplane can cause intermittent module communication errors that are difficult to diagnose without knowing the chassis condition.
Module seating: SLC 500 modules use a lever-and-latch mechanism. Modules that have been inserted and removed many times can develop loose engagement. Gently reseat any module that produces intermittent I/O faults before assuming the module itself has failed.
Program backup: always keep a current backup of the SLC program in RSLogix 500 format (.RSS file) in at least two separate locations. A CPU module replacement without a program backup requires the program to be reconstructed from scratch or recovered from a specialist — an expensive and time-consuming process.
Spare parts kit: a minimum spare parts set for a critical SLC system includes the CPU module, the power supply, and a sample of the most frequently failing I/O modules (typically the highest-cycle relay output modules and any modules in harsh environments). The chassis itself is worth one spare if the system is production-critical.

FAQ

Q: Can the 1746-A10 be used with a fixed SLC 500 controller (1747-L20 etc.) instead of a modular CPU?

No. Fixed SLC 500 controllers are standalone units with their own integrated I/O — they don't mount into a 1746 chassis. The 1746-A10 is for modular SLC 500 CPUs (1747-L40, L541, L551, etc.) that slot into the chassis as a separate module.

Q: Is a 10-slot chassis always better than a smaller chassis for flexibility?

Not necessarily. A smaller chassis with fewer empty slots is slightly simpler to maintain and may fit better in a constrained panel. For a known I/O count that's unlikely to grow, the right-sized chassis is usually better than an oversized one. The practical advantage of a larger chassis appears when the application is likely to expand or when spare slots for future modules are genuinely anticipated.

Q: Can I/O modules be hot-swapped in the 1746-A10 chassis?

The SLC 500 platform does not officially support hot-swap on standard I/O modules. Some experienced users remove and insert modules under power for emergency repairs, but this risks corrupting the backplane communication state and potentially damaging the module or CPU. Best practice is to de-energize the chassis before removing or inserting any module.

Q: Is the 1746-A10 compatible with SLC 5/03, 5/04, and 5/05 processors?

Yes. All SLC 5/0x modular processor variants (5/01 through 5/05) use the same 1746 chassis form factor and backplane connection. The 1746-A10 is compatible with all of them. Processor capability (memory, scan time, communication options) varies by processor model, but the chassis itself is processor-agnostic within the 1746 series.

Q: What power supply is needed for the 1746-A10?

The SLC 500 power supply module (1746-P2, P3, P4, or P7 depending on input voltage and output current requirements) installs in Slot 0. Select the power supply based on the AC or DC input voltage available and the total current demand of the installed modules — add up the 5V and 24V backplane current draws from all modules to verify the supply is not overloaded.

1746-A10 New Sealed 1746A10 Ser B Chassis/Rack 10 Slots Module