Allen-Bradley PLC-5: Replacement & Cross-Reference

The Allen-Bradley PLC-5 (1785-L series) is a discontinued large PLC platform. Rockwell's migration path is ControlLogix (1756), with conversion tools from RSLogix 5 to Studio 5000 and options to keep DH+ and 1771 I/O during a phased cutover. For plants holding PLC-5 lines, Edmundson Industrial sources new-surplus, used-tested, and reconditioned PLC-5 processors, 1771 I/O, and chassis.

Status

Brand	Allen-Bradley / Rockwell Automation
Family	PLC-5 (1785 series)
Common catalog numbers	1785-L11B, L20B, L40B, L60B, L80B · 1785-L40E / L80E (Ethernet) · 1771 I/O
Lifecycle	Discontinued / end-of-life: verify current Rockwell status at quote
Programming	RSLogix 5 (legacy)

Cross-Reference

If you have (obsolete)	Recommended path	Notes
PLC-5 processor (1785-L…)	ControlLogix 1756-L8	Convert RSLogix 5 to Studio 5000; plan the I/O strategy and checkout time.
PLC-5 on a DH+ network	ControlLogix with DH+ bridge (1756-DHRIO)	Keep DH+ / RIO devices during a phased migration.
1771 I/O	Reuse on migration, or like-for-like surplus	1771 reuse paths exist; confirm module support when planning.
Keep the program: no re-engineering	New-surplus / used-tested PLC-5 (we source)	Keeps the installed program. Match processor memory, comms, and series/revision.

Cross-references are starting points: confirm processor memory, communications, and program compatibility before substituting. We'll verify on request.

Key Specs

Large rack-based PLC using 1771 I/O
Communications: DH+, Remote I/O (RIO), RS-232, and Ethernet on E models
Battery-backed memory; processor sizes from 1785-L11B to L80B
Programmed in RSLogix 5; does not convert directly to Studio 5000 without tools
Confirm processor series/revision and channel configuration on the nameplate

Is the PLC-5 still made?

No. ControlLogix is the successor platform. PLC-5 still runs major process, utility, and heavy-industry systems, so spares, processor, 1771 I/O, memory battery, buy time to migrate on a planned schedule rather than during an outage. We source the originals and quote the ControlLogix path.

FAQ

Is the Allen-Bradley PLC-5 discontinued?

Yes: the PLC-5 platform is discontinued. New-surplus, used-tested, and reconditioned processors and 1771 I/O remain available through Edmundson Industrial.

What replaces a PLC-5?

ControlLogix (1756) is Rockwell's migration path. Programs convert from RSLogix 5 to Studio 5000, and DH+/RIO devices can be bridged during a phased cutover.

Can I still buy PLC-5 processors and I/O?

Yes: we source 1785 processors, 1771 I/O, chassis, and memory modules in new-surplus and used-tested condition.

Can I reuse my 1771 I/O when migrating?

Often, yes: reuse paths to ControlLogix exist for many 1771 modules. Confirm specific module support when planning.

What do you need to quote PLC-5 parts?

Catalog numbers (1785-…, 1771-…) or nameplate photos, acceptable condition, and your need-by date.

Availability & Quote

Condition disclosed before sale, new-surplus, used-tested, or reconditioned, with photos on request.

Request a Quote

or send catalog numbers to sales@edmundsonindustrial.com · (832) 975-8827 · Houston, TX. Response timing is confirmed with the request.

Related Allen-Bradley legacy pages

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