Allen-Bradley 1747-L551 SLC 500 Processor
In stock: 8 units in Milwaukee, WI. Physically stocked and ready to ship or available for local pickup. Includes a 1-year full-function warranty.
SLC 5/05 PLC Processor · 16K Words User Memory · channel 0 RS-232 (DF1 / DH-485 / ASCII) and channel 1 Ethernet (10Base-T; 10/100 on later series)
Actual NJT inventory photos
Starting at
$1,129.99USD
Used and refurbished options available
| Part Number | 1747-L551 |
| Description | SLC 5/05 PLC Processor. In stock in used and refurbished condition, Series C and D. |
| Shipping | Ships same or next business day UPS Ground included | Next-Day Air and Worldwide Shipping available at checkout |
| Pickup | Free local pickup at 2122 N Prospect Ave. Call ahead at (414) 331-5954. |
| Warranty | 1-year full-function warranty provided by NJT Automation. Warranty details
|
| Returns | 90-day free returns. View return policy |
| Exchange | Send us your defective 1747-L551 after your purchase for a 10% core credit (from $113). We also purchase old or damaged parts outright. |
Replacement Options for 1747-L551
Pick a condition and series below. UPS Ground shipping included.
| Variants | Part NumberConditionSeriesQtyPrice 1747-L551 /C$1,129.99 Used · Series C · 1 in stock1747-L551 /CUsedSeries C1$1,129.99 USD 1747-L551 /C$1,199.99 Used · Series C · 1 in stock1747-L551 /CUsedSeries C1$1,199.99 USD 1747-L551 /C$1,349.99 Refurbished · Series C · 4 in stock1747-L551 /CRefurbishedSeries C4$1,349.99 USD 1747-L551 /C$1,419.99 Refurbished · Series C · 1 in stock1747-L551 /CRefurbishedSeries C1$1,419.99 USD 1747-L551 /D$1,999.99 Used · Series D · 1 in stock1747-L551 /DUsedSeries D1$1,999.99 USD | ||||||||||||||||||||||||||
| Availability | 8 units in stock | ||||||||||||||||||||||||||
| Repairs | 1747-L551 Mail-In Repair Service | Flat RateFlat rate: $949.99 | ||||||||||||||||||||||||||
Part Number Decoder | SLC 5/05 PLC Processor 1747L551
Decoded from the Rockwell Automation catalog-number structure. Series and firmware revision are printed on the product label, not encoded here. | ||||||||||||||||||||||||||
Series & Revisions | Series C and D in stock; other series on request. Series A shipped with OS500 and can be flashed to OS501; Series B and C ship with OS501. Only Series C hardware has the 10/100 Mbps Ethernet port; A and B run 10 Mbps half duplex. Series notes: Same slot and wiring. A later series runs an earlier program; an earlier series rejects a program that uses newer OS/FRN features. | ||||||||||||||||||||||||||
Intended Use | Designed for Ethernet-connected legacy machine and small-process control applications. SLC 500 processors still run packaging lines, conveyors, water and wastewater stations, HVAC plants and OEM machinery installed through the 1990s and 2000s. Most demand today is replacing a failed processor like-for-like so the existing rack, I/O and RSLogix 500 program stay in place. | ||||||||||||||||||||||||||
Migration Path | Rockwell Automation has discontinued SLC 500 processors; replacement units come from the surplus market. Published successor for the SLC 500 modular processor: CompactLogix 5380 (5069-L3xxER) with Compact 5000 I/O, or CompactLogix 5370 (1769-L3xER) to reuse 1769 Compact I/O.
A like-for-like replacement or a repair keeps the existing program, wiring and panel layout; a migration is a project. Both are listed on this page so the choice can be made on lead time and budget. | ||||||||||||||||||||||||||
Physical Data | Weight and DimensionsEst. weight0.82 lb (0.37 kg)H × W × D5.7 × 1.4 × 5.7 in. (145 × 35 × 145 mm)
Product dimensions are typical manufacturer-published values and may differ by series or option. Unit weight is an estimate; no published figure is available for this catalog number. Shipping box and weight are estimates for freight planning; the packed unit may ship in a different box. | ||||||||||||||||||||||||||
Similar Part Numbers | |||||||||||||||||||||||||||
Allen Bradley Information | Technical Specifications12 parameters from manufacturer-published specifications
Typical manufacturer-published values for this catalog number; confirm against the current manufacturer documentation before specifying. | ||||||||||||||||||||||||||
| Category | SLC 500 | ||||||||||||||||||||||||||
| UPC / GTIN | 10662072745622 | ||||||||||||||||||||||||||
| Part Number | 1747-L551 | ||||||||||||||||||||||||||
| Manufacturer | Allen-Bradley | ||||||||||||||||||||||||||
Previously sold 1747-L5517 sold
NJT Automation has supplied and shipped 7 1747-L551 SLC 5/05 PLC Processors since 2024; these listings are sold and the in-stock options above are ready to ship.
- Sold
- 7 since 2024
- Series
- A × 3, B × 2, C × 2
Can the 1747-L551 be repaired?
Yes. NJT Automation repairs the 1747-L551 by mail-in: diagnostic evaluation, component-level repair and a functional test, backed by a 1-year full-function warranty.
NJT managed repair. No evaluation fee; no repair, no charge. Prepaid UPS label both ways, $650 minimum, rush available. 1-year full-function warranty included, 2- and 3-year options.
Compare quotes from independent repair technicians. Post your repair on RepairMode to receive competitive bids from experienced technicians. Each technician sets their own pricing and warranty.
View completed 1747-L551 repairson RepairMode.com ↗Common failures
Failure patterns we regularly see on SLC 5/05 PLC Processor hardware like the 1747-L551:
- FLT LED on and the processor will not go to RUN (major fault that returns after clearing)
- DH+ channel 1 dead on a 5/04 (transceiver failure on the 3-pin blue-hose port)
- Keyswitch worn: processor will not stay in RUN or REM
- Program lost on power cycle: BATT LED on, battery (1747-BA) depleted
- Channel 0 RS-232 port damaged by a hot-plugged or miswired programming cable
Photos by NJT Automation; test videos from NJT or network repair technicians.
Still have questions?
Find answers to shipping, warranties, repairs, and more.