1756-A7 — 1756 Seven-Slot Logix Chassis

The 1756-A7 is a 7-slot chassis for the 1756 Logix modular control system. It provides the physical housing and backplane that connects the power supply, processor, communication modules, and I/O modules in a 1756 system. The chassis itself contains no processing logic — it is the structural and electrical backbone that all 1756 modules plug into. Seven slots accommodate a processor in Slot 0 and up to six modules in Slots 1–6, making it suitable for small-to-medium controller builds that don't require the larger 10, 13, or 17-slot chassis.

Specifications

Parameter	Value
Part Number	1756-A7
Platform	1756 Logix modular system
Total Slots	7
User Module Slots	6 (Slot 0 = processor; Slots 1–6 = I/O / comm modules)
Backplane	1756 series parallel backplane
Power Supply Slot	Left end (dedicated, outside the 7-slot count)
Module Compatibility	All 1756-series I/O, communication, and specialty modules
Mounting	Panel surface or DIN rail adapter
Enclosure	Open chassis (requires panel enclosure)
Operating Temperature	0°C to 60°C
Standards	UL 508, CE

Backplane Power Budget

The 1756 power supply module (selected separately) provides both 5V DC and 24V DC to the backplane. Each module installed in the chassis draws a defined amount of current from each rail — these values are listed in each module's specifications. The sum of all modules' 5V draw must not exceed the power supply's 5V capacity, and similarly for the 24V rail.

Before finalizing a chassis build, add up the backplane current draws for all planned modules and compare against the chosen power supply's ratings. Common misses: EtherNet/IP communication modules draw significantly more 5V current than simple I/O modules; multiple high-density output modules switching simultaneously can draw more 24V rail current than expected. The 1756-PA75 (75W AC) and 1756-PB75 (75W DC) are the standard power supplies for the 7-slot chassis — verify the total current demand fits within their rated output.

The power supply module for the 1756-A7 is ordered separately — it does not ship with the chassis. The 1756-PA75R (AC) or 1756-PB75R (DC) redundant variants can also be used when supply redundancy is required. Verify the power supply catalog number matches the available panel supply voltage (AC or DC) before ordering.

FAQ

Q: Can the 1756-A7 be used in a remote chassis configuration over EtherNet/IP?

Yes. Install a 1756-EN2T or 1756-EN4TR communication module in the chassis and configure it as a remote I/O chassis in Studio 5000. The processor in the remote chassis can be a communication bridge module (not a full processor) if no local processing is needed — the remote chassis then functions purely as an I/O expansion rack.

Q: Is the power supply slot included in the 7-slot count?

No. The power supply occupies a dedicated slot at the left end of the chassis that is not counted in the 7 module slots. All 7 slots are available for the processor and other modules.

Q: Can I/O modules be hot-swapped in the 1756-A7?

Yes, in systems configured for module hot-swap. The 1756 chassis and 1756-L7x/L8x processors support module removal and insertion under power. Verify the controller's I/O module configuration and the machine's interlocks permit a safe swap before removing a module from a running system.

Q: What is the difference between the 1756-A7 and the 1756-A7K?

The 1756-A7K is a conformal-coated variant for installations in environments with humidity, condensation, or mild chemical exposure that would degrade an uncoated chassis. Mechanically and electrically identical — the conformal coating is the only difference. Use the K variant where IPC-CC-830B conformal coating is required by the installation specification.

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