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Brand: Allen-Bradley
Allen-Bradley 1756-L73 ControlLogix 5570 Controller 8 MB
Description
The 8 MB ControlLogix 5570 controller and its sibling sizes
The Allen-Bradley 1756-L73 is the 8 MB member of the ControlLogix 5570 controller range, the generation that preceded the 5580 and is still widely installed in Gulf refinery, power and water plants. Rockwell Automation now lists it as Active Mature, which makes it a typical spare when an existing rack must be kept running without a controller upgrade.
One technical-data table covers the whole L71 to L75 series, so the memory sizes below are the quickest way to confirm that the L73 is the right step for a replacement: the sizes differ, while I/O limits, power draw and the chassis list stay the same. For maintenance teams this matters in practice: a project written for a 16 MB L74 will not download into an L73 if the program and tag data exceed 8 MB, so memory use should be read from the project before a replacement is chosen.
Technical specifications
| Parameter | Specification |
|---|---|
| Catalog number | 1756-L73 (conformal-coated 1756-L73K listed separately) |
| User memory | 8 MB (series: L71 2 MB, L72 4 MB, L73 8 MB, L74 16 MB, L75 32 MB) |
| I/O memory | 0.98 MB |
| Digital I/O, max | 128,000 |
| Analog I/O, max | 4000 |
| Controller connections, max | 500 |
| Built-in port | 1 USB 2.0 full-speed port, programming/configuration/firmware update/online edits only |
| Non-volatile memory | 1 GB Secure Digital card (1784-SD1), pre-installed |
| Energy storage | 1756-ESMCAP capacitor module ships installed; NSE and non-removable variants available |
| Backplane current | 5 mA at 1.2 V DC; 800 mA at 5.1 V DC |
| Power dissipation | 2.5 W (8.5 BTU/hr) |
| Isolation | 30 V continuous, basic insulation, USB port to system |
| Weight, approx | 0.25 kg (0.55 lb) |
| Slot width / location | 1 slot, any slot of a 1756 chassis |
| Tasks | 32 tasks, up to 1000 programs per task |
| Programming languages | Ladder, structured text, function block, sequential function chart |
| Enclosure / temperature code | Open-style; T4 |
Communication and system options
The L73 has no Ethernet port of its own. Networks are added with separate 1756 modules in the same chassis: EtherNet/IP through 1756-EN2T, EN2TR, EN3TR or EN4TR, ControlNet through the CN2 family, DeviceNet, Data Highway Plus, remote I/O and SERCOS. The technical data gives module connection limits such as 1000 I/O and 528 EtherNet/IP connections on a 1756-EN4TR and 256 on a 1756-EN2x. Integrated motion on EtherNet/IP and controller redundancy are supported. The environmental table gives 0 to +60 C operating and -40 to +85 C non-operating temperature, 5 to 95 percent non-condensing humidity, and the module carries the UL, CE, ATEX and IECEx marks printed in the manufacturer certification table.
Replacement and selection guidance
Before ordering, check the firmware revision your Studio 5000 or RSLogix 5000 project needs, the SD card size, and whether the existing chassis is Series B or C. If you are planning a new installation, ask whether a 5580 controller such as the 1756-L83E suits better, since it carries the Ethernet port on the controller itself. The data on this page is drawn from the manufacturer publication and is meant as a starting point; confirm the catalog number, suffix and series with the installed module label.
Documents and quotation
The linked technical data covers every ControlLogix and GuardLogix controller in one publication. See other automation hardware in the PLC & I/O Cards category, or send your catalog number list to Seven Star LLC, an independent supplier in Muscat, to request a quotation.
Datasheets & Documents
- Technical data Rockwell Automation 1756 ControlLogix and GuardLogix Controller Specifications, publication 1756-TD001 Download
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About brand
Allen-Bradley is the brand of Rockwell Automation for industrial control: ControlLogix and CompactLogix controllers, I/O systems, PanelView operator terminals, PowerFlex drives, motor control and industrial network equipment. The company began in Milwaukee in 1903, when Lynde Bradley and Dr. Stanton Allen formed the Compression Rheostat Company to make the motor speed controller Bradley had invented in 1901. It took the name Allen-Bradley in 1909 and was bought by Rockwell International in 1985. Since 2001 its owner has been Rockwell Automation, which is still headquartered in Milwaukee, Wisconsin.
Allen-Bradley company profile
| Founded | 1903, Milwaukee, Wisconsin, USA, as the Compression Rheostat Company |
|---|---|
| Founders | Lynde Bradley (inventor of the compression rheostat, 1901) and Dr. Stanton Allen (investor); Harry Bradley joined in 1904 |
| Name | Allen-Bradley Company from 1909 |
| Ownership | Acquired by Rockwell International in 1985 for about USD 1.65 billion; a brand of Rockwell Automation (NYSE: ROK) since 2001 |
| Headquarters | Milwaukee, Wisconsin, USA |
| Product families | Logix programmable automation controllers (ControlLogix, CompactLogix), legacy SLC 500 and MicroLogix PLCs, Micro800 controllers, POINT, FLEX and Compact I/O, PanelView HMIs, PowerFlex AC drives, contactors, motor starters and soft starters, safety components, Stratix Ethernet switches |
Milestones
- 1901: Lynde Bradley invents the compression rheostat to control the speed of electric motors.
- 1903: The Compression Rheostat Company is formed in Milwaukee with an initial investment of USD 1,000.
- 1904: Harry Bradley joins; a crane controller is shown at the St. Louis World's Fair.
- 1909: The company is renamed Allen-Bradley.
- 1985: Rockwell International acquires Allen-Bradley.
- 2001: Rockwell Automation becomes the company's name; the Allen-Bradley brand marks 100 years in 2003.
Reading Allen-Bradley catalogue numbers
The first digits of an Allen-Bradley catalogue number identify the platform, which tells you what is compatible with what. 1756 is ControlLogix (chassis-based, used for large process and plant control), 1769 is CompactLogix 5370 with Compact I/O, 5069 is CompactLogix 5380 with Compact 5000 I/O, 1734 is POINT I/O, 1794 and 5094 are FLEX and FLEX 5000 distributed I/O, 1746 and 1747 belong to the older SLC 500 family, 1766 is MicroLogix 1400 and 2080 is Micro800. For drives, 25B is PowerFlex 525 and 22B is PowerFlex 40; in a code such as 25B-D010N114, "D" means 380–480 V, "010" is the output current rating, and N114 instead of N104 means the drive has an integrated EMC filter. Many plants in the region still run SLC 500 and older MicroLogix systems, which Rockwell has discontinued, so exact spares and migration to CompactLogix are both common requests.
Where Allen-Bradley products are used
In Oman and the GCC, Allen-Bradley controllers and drives run on oil and gas facilities, water treatment and pumping stations, cement, food and beverage and packaging plants, and on machines supplied by American OEMs. ControlLogix is often the platform for plant control systems, while PowerFlex drives are used on pumps, fans and conveyors.
Allen-Bradley products we list
| Family | Examples |
|---|---|
| ControlLogix | 1756-L85E, 1756-EN2T, 1756-EN2TR, 1756-IF16, 1756-IB32, 1756-PA75, 1756-A10 |
| CompactLogix and Micro controllers | 5069-L320ER, 5069-L340ERM, 1769-L33ER, 1769-L16ER, MicroLogix 1400, Micro820, SLC 500 (1746) |
| Distributed I/O | 1734-AENTR, 1734-IB8, 1734-IE2C, 1734-IB8S safety, 1794-AENTR, 5094-AENTR, 5069-IF8 |
| Operator terminals | PanelView Plus 7 10-inch, PanelView Plus 7 15-inch, PanelView 800, PanelView 5310 |
| Drives, motor control and networking | PowerFlex 525, PowerFlex 755, PowerFlex 4, 150-A180NBD SMC, Stratix 2000, 1783-NATR |
Ordering Allen-Bradley products: what we need
Send the full catalogue number and the series letter from the label (for example 1756-EN2T Series D), because firmware and compatibility can change between series. For drives, add the motor power, voltage and filter option. For a discontinued SLC 500 or MicroLogix part, tell us whether you need the exact spare or a migration proposal.
Facts checked against Rockwell Automation's published company history, October 2026.
Browse Allen-Bradley products by category: PLC & I/O Cards, AC Drives.
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Frequently Asked Questions
What is the memory of the 1756-L73?
8 MB of user memory, with 0.98 MB of I/O memory.
Does the L73 have an Ethernet port?
No. It has a USB port only; EtherNet/IP is added with a separate 1756-EN module in the chassis.
How many I/O points can it address?
Up to 128,000 digital and 4000 analog points, with 500 controller connections.
What storage card does it use?
A pre-installed 1 GB SD card, 1784-SD1; larger cards may be available per the manufacturer.
Is it still an active product?
The product page lists it as Active Mature, so confirm availability and the preferred replacement before ordering.
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