Allen-Bradley 1756-L81E ControlLogix Processor 3 MB – Pickup in Store
In stock: 2 units in Milwaukee, WI. Physically stocked and ready to ship or available for local pickup. Includes a 1-year full-function warranty.
3 MB ControlLogix 5580 controller · embedded 1 Gb EtherNet/IP port
Actual NJT inventory photos
Starting at
$2,499.99USDRefurbished, Series BView listing
Refurbished and unused surplus options available below
| Part Number | 1756-L81E |
| Description | ControlLogix 5580 controller, 3 MB. In stock in refurbished and unused surplus condition, Series B. |
| Shipping | Ships same or next business day
|
| 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
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| Returns | 90-day free returns. View return policy |
| Exchange | Send us your defective 1756-L81E after your purchase for a 10% core credit. We also purchase old or damaged parts outright. |
Replacement Options for 1756-L81E
| Variants | |||||||||||||||||||||||||||||||||
| Availability | 2 units in stock | ||||||||||||||||||||||||||||||||
| Repairs | 1756-L81E Mail-In Repair ServiceEstimated: $1,440.00 | ||||||||||||||||||||||||||||||||
Part Number Decoder | ControlLogix 5580 controller 1756L81E
Decoded from the Rockwell Automation catalog-number structure. Series and firmware revision are printed on the product label, not encoded here. | ||||||||||||||||||||||||||||||||
Series & Revisions | Series B in stock; other series on request. Series B controllers run firmware revision 31.011 or later; Series A units also run the earlier 5580 revisions (28 to 30). Every series needs a Series B or Series C 1756 chassis (Series B derated to 50 °C ambient); 5580 controllers do not work in a Series A chassis. Series notes: Studio 5000 keys on catalog number and firmware revision, not series. Fitting a Series B into a project on revision 28 to 30 means upgrading the project to 31 or later first. | ||||||||||||||||||||||||||||||||
Intended Use | Designed for plant-wide discrete, process, and motion control applications. ControlLogix controllers run high I/O-count machines, batch and continuous process lines, and coordinated multi-axis motion from a single chassis, with redundancy and plant-network connectivity when the application calls for it. Typical homes are automotive and tire plants, food and beverage lines, water and wastewater, oil and gas skids, and large packaging systems. | ||||||||||||||||||||||||||||||||
Physical Data | Weight and DimensionsWeight0.87 lb (0.39 kg)H × W × D5.7 × 1.4 × 5.7 in. (145 × 35 × 145 mm)
Product weight and dimensions are typical manufacturer-published values and may differ by series or option. 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 Specifications15 parameters from manufacturer-published specifications
Typical manufacturer-published values for this catalog number; confirm against the current manufacturer documentation before specifying. | ||||||||||||||||||||||||||||||||
| Category | ControlLogix | ||||||||||||||||||||||||||||||||
| UPC / GTIN | 887172361326 | ||||||||||||||||||||||||||||||||
| Part Number | 1756-L81E | ||||||||||||||||||||||||||||||||
| Manufacturer | Allen-Bradley | ||||||||||||||||||||||||||||||||
Previously sold 1756-L81E5 sold · +14 on eBay
NJT Automation has supplied and shipped 5 1756-L81E ControlLogix 5580 controllers since 2024; these listings are sold and the in-stock options above are ready to ship.
- Sold
- 5 since 2024
- Series
- B × 5
Image gallery62 PHOTOSActual units photographed by NJT
Can the 1756-L81E be repaired?
Yes. NJT Automation repairs the 1756-L81E by mail-in: diagnostic evaluation, component-level repair and a functional test, backed by a 1-year full-function warranty.
Option 1
NJT managed repair
- Evaluation
- Free. No repair, no charge.
- Shipping
- Prepaid UPS label both ways.
- Pricing
- $650 minimum. Rush service available.
- Warranty
- 1-year full-function warranty included; 2- and 3-year options.
Option 2
Independent repair bids. 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.
Common Failures
Failure patterns we regularly see on ControlLogix 5580 controller hardware like the 1756-L81E:
- SD card corruption: controller reports a load failure or comes up with no project
- Controller will not boot or shows a solid red OK LED (nonrecoverable major fault) after a power event
- Repeated major faults after a firmware flash that did not complete
- Overheating in a full chassis, especially with no spacing in sealed enclosures
- Four-character status display stuck, blank or showing scrolling fault text
Fault code reference
1756-L81E Fault Codes
42 codes · 1756-RD001
Fault codes a ControlLogix 5580 controller reports on the Major Faults tab in Studio 5000 Logix Designer / RSLogix 5000 as Type:Code (T:C), as documented in Rockwell Automation publication 1756-RD001. Use them to narrow a problem down to the unit, its wiring or the application before sending it in for repair.
| Code | Fault | What it indicates |
|---|---|---|
| T01:C01 | Power-up fault | Power was lost and restored while the controller was in RUN mode. |
| T01:C16 | Power-up fault | I/O communications configuration fault detected at power-up. |
| T01:C40 | Power-up fault | Energy storage module or battery failed during the last power-down; retained data may be lost. |
| T01:C60 | Power-up fault | Non-recoverable fault. The controller must be reflashed or returned for repair. |
| T01:C61 | Power-up fault | Non-recoverable fault with saved diagnostic information. |
| T01:C62 | Power-up fault | Non-recoverable fault with saved diagnostic information and stored user program. |
| T03:C16 | I/O fault | An I/O module connection failed on a module marked as required. |
| T03:C20 | I/O fault | Unable to read ControlBus chassis information; the chassis may be bad. |
| T03:C21 | I/O fault | Unable to read ControlBus chassis information; the chassis may be bad. |
| T03:C23 | I/O fault | At least one required connection was not established before going into RUN mode. |
Show 32 more codes
| T04:C16 | Program fault | Unknown instruction encountered. |
| T04:C20 | Program fault | Array subscript too large, or CONTROL data type POS or LEN invalid. |
| T04:C21 | Program fault | CONTROL data type LEN or POS less than 0. |
| T04:C24 | Program fault | Unknown data type passed to a subroutine. |
| T04:C31 | Program fault | JSR or RET did not pass as many parameters as expected. |
| T04:C34 | Program fault | A timer instruction had a negative value for its PRE or ACC. |
| T04:C42 | Program fault | JMP to a label that did not exist or was deleted. |
| T04:C82 | Program fault | Could not re-enter an executing SFC routine. |
| T04:C83 | Program fault | Value out of range. |
| T04:C84 | Program fault | Stack overflow: stack too small to perform the operation. |
| T04:C85 | Program fault | Invalid routine type. |
| T04:C89 | Program fault | Target step does not exist in the specified routine. |
| T04:C90 | Program fault | A safety instruction occurs outside a safety task. |
| T04:C91 | Program fault | Equipment phase instruction cannot be called from a program. |
| T04:C94 | Program fault | Nesting limits exceeded. |
| T04:C990–C999 | Program fault | User-defined major fault raised by the application. |
| T06:C01 | Watchdog fault | Task watchdog expired: an infinite loop, an over-complex program or a higher-priority task starved the task. |
| T07:C40 | Nonvolatile fault | Store to nonvolatile memory (CompactFlash / SD) failed. |
| T07:C41 | Nonvolatile fault | Load from nonvolatile memory failed: controller type mismatch. |
| T07:C42 | Nonvolatile fault | Load from nonvolatile memory failed: controller revision mismatch. |
| T07:C43 | Nonvolatile fault | Load from nonvolatile memory failed: bad checksum. |
| T07:C44 | Nonvolatile fault | Failed to restore processor memory. |
| T07:C50 | Nonvolatile fault | Security certificate invalid. |
| T08:C01 | Mode change fault | Mode change inhibited because a download is in progress. |
| T11:C01 | Motion fault | Actual position of the axis exceeded the positive overtravel limit. |
| T11:C02 | Motion fault | Actual position of the axis exceeded the negative overtravel limit. |
| T11:C03 | Motion fault | Actual position exceeded the position error tolerance. |
| T11:C04 | Motion fault | Encoder channel A, B or Z connection failed. |
| T11:C05 | Motion fault | Encoder noise event detected, or encoder signals not in quadrature. |
| T11:C06 | Motion fault | Drive fault reported by the servo drive. |
| T11:C07 | Motion fault | Synchronous connection to the servo module failed. |
| T11:C08 | Motion fault | Hardware failure in the servo module. |
Where the manual's only remedy for a code is to replace the unit or module, the code is pointing at a hardware fault inside that part. Those are the faults NJT Automation repairs at component level, so a repair quote is usually the first thing to check before buying a replacement.
Source: Rockwell Automation publication 1756-RD001, Logix 5000 Controller and I/O Fault Codes. Codes are listed as documented; fault behaviour can vary by firmware revision, so confirm against the manual for your unit's series.
Photos by NJT Automation; test videos from NJT or network repair technicians.
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