Allen-Bradley 1775-LX Communication Adapter Module | Replacement, Equivalent & Selection Guide
The Allen-Bradley 1775-LX is a Communication Adapter Module designed for use within the Allen-Bradley PLC-3 family of programmable logic controller systems. It provides the physical and logical interface layer that enables the PLC-3 processor to communicate across industrial networks, supporting reliable data exchange in demanding automation environments.
This page serves as a comprehensive replacement and equivalent selection guide for engineers, procurement specialists, and MRO buyers who need to source, substitute, or cross-reference the 1775-LX — whether for emergency replacement, lifecycle upgrade, or cross-brand evaluation.
Technical Specifications
| Parameter | Specification | Replacement Impact |
|---|---|---|
| Part Number | 1775-LX | Primary cross-reference key |
| Manufacturer | Allen-Bradley (Rockwell Automation) | OEM baseline |
| Module Type | Communication Adapter Module | Must match for drop-in replacement |
| Compatible Platform | PLC-3 Series | Critical — platform-specific |
| Communication Protocol | Data Highway / DH+ | Must verify protocol match |
| Backplane Interface | PLC-3 I/O chassis backplane | Physical slot compatibility required |
| Operating Temperature | 0°C to 60°C | Verify for harsh environments |
| Power Consumption | Per PLC-3 chassis spec | Check chassis power budget |
| Weight | 1,800 g (approx.) | — |
| Firmware | Factory-loaded, revision-specific | ⚠ Verify firmware revision before substitution |
Compatible Replacement & Equivalent Models
When sourcing a replacement or equivalent for the 1775-LX, buyers must evaluate three tiers of compatibility. Always verify firmware revision, chassis slot count, and network protocol before committing to a substitute.
1. Direct Drop-in Replacements
These are OEM or certified-refurbished units of the same part number. A genuine Allen-Bradley 1775-LX sourced from an authorized distributor or reputable MRO supplier is the safest drop-in replacement. No configuration changes are required provided the firmware revision matches the existing system.
2. Functional Equivalents (Same Platform)
Within the PLC-3 family, certain communication adapter variants may offer equivalent functionality depending on the network topology in use. Buyers should consult the PLC-3 system manual (publication 1775-6.4.1) to identify approved adapter variants. Note: Functional equivalents may require minor parameter reconfiguration in RSLogix or the legacy 6200 programming software.
3. Cross-Brand Alternatives
For system migrations or lifecycle replacements where PLC-3 hardware is being phased out, cross-brand alternatives include modern communication gateways (e.g., ProSoft Technology MVI series, Moxa industrial converters) that can bridge legacy DH+ networks to Ethernet/IP or PROFIBUS. Important: Cross-brand alternatives are not drop-in replacements — they require engineering evaluation, gateway configuration, and potential PLC program modifications. Contact Konmask for a migration assessment.
Why Choose the Original Model
- Precision Compatibility: The 1775-LX is engineered to exact PLC-3 backplane and protocol specifications — no adaptation layer, no signal degradation risk.
- Certified & Compliant: Carries original UL/CE certifications applicable to the PLC-3 platform, ensuring regulatory compliance in certified installations.
- Firmware Integrity: Factory-loaded firmware is revision-matched to the PLC-3 OS, eliminating the risk of version mismatch that can cause communication faults.
- Full System Compatibility: Guaranteed interoperability with all PLC-3 chassis, power supplies, and I/O modules without additional testing or validation.
- OEM Technical Support: Rockwell Automation’s TechConnect support covers original hardware; third-party substitutes may void support agreements.
- Warranty & Traceability: Konmask supplies units with documented sourcing traceability and a minimum 12-month warranty, protecting your maintenance budget.
Typical Applications
- Automotive Manufacturing: Body-in-white assembly lines using legacy PLC-3 controllers for coordinated multi-axis motion and conveyor control.
- Oil & Gas Processing: Upstream and midstream facilities where PLC-3 systems manage valve sequencing and pipeline monitoring over DH+ networks.
- Power Generation: Turbine control and switchgear automation systems requiring high-reliability communication adapters with proven field history.
- Water & Wastewater Treatment: SCADA-integrated pump station control where PLC-3 platforms remain in service under long asset lifecycle policies.
- Food & Beverage Processing: Batch control and CIP (clean-in-place) systems on legacy Allen-Bradley platforms pending full modernization.
- Mining & Minerals: Conveyor drive control and crusher automation in remote sites where proven legacy hardware is preferred over new platform risk.
System Compatibility
The 1775-LX is designed to operate within the following Allen-Bradley PLC-3 ecosystem components:
- 1775-A3 / 1775-A4 / 1775-A7: PLC-3 I/O chassis (3, 4, and 7-slot) — physical host for the adapter module.
- 1775-ME / 1775-MED: PLC-3 Processor Modules — the CPU units that the 1775-LX serves as a communication interface for.
- 1775-S4A / 1775-S4B: PLC-3 Power Supply Modules — must provide adequate power budget for the adapter.
- 1770-KF2 / 1770-KF3: Data Highway Interface Modules — network-side counterparts for DH+ topology.
- 1785-KA / 1785-KA5: Communication Adapter Modules for PLC-5 (cross-reference for migration planning).
- 6200 Series Programming Software / RSLogix 3: Programming and configuration tools compatible with the 1775-LX communication layer.
Selection Guide
Use these three questions to confirm the 1775-LX — or its equivalent — is the right choice for your application. If any answer is uncertain, contact Konmask before ordering.
Q1: Is your existing controller a PLC-3 series unit (1775-ME or 1775-MED processor)?
If yes, the 1775-LX is the correct OEM communication adapter. If you are running a PLC-5 or ControlLogix platform, a different adapter family is required — contact us for the correct cross-reference.
Q2: Does your network topology use Data Highway (DH) or DH+ protocol?
The 1775-LX is optimized for DH/DH+ communication. If your facility has migrated to Ethernet/IP or DeviceNet, a gateway solution or platform upgrade may be a more cost-effective substitute. Konmask can advise on compatible migration paths.
Q3: What is the firmware revision of your existing PLC-3 system?
Firmware revision mismatches between the adapter and processor can cause communication faults. Provide your processor series and firmware revision when ordering so Konmask can match or verify the replacement unit accordingly.
Quality Assurance & Sourcing
Sourcing Channels: Konmask sources the 1775-LX through authorized Allen-Bradley distributors, certified MRO surplus channels, and factory-refurbished stock with full documentation. We do not supply counterfeit or unmarked units.
4-Step Inspection Process:
- Visual Inspection: Board-level examination for physical damage, corrosion, counterfeit markings, and date code verification.
- Functional Test: Bench-level power-on and communication handshake test using a reference PLC-3 chassis.
- Firmware Verification: Revision check and documentation against the unit’s label and internal registers.
- Final QC & Packaging: ESD-safe packaging, serialized QC label, and shipment with inspection report.
Available Documentation: Certificate of Conformance (CoC), inspection report, sourcing declaration, and — where available — original Rockwell Automation test records.
How to Order
- Submit Your Requirement: Email support@konmask.com or call +0086 19859288691 with your part number (1775-LX), required quantity, and any firmware revision or lead-time constraints.
- Receive Quotation & Availability Confirmation: Konmask will respond within 24 hours with pricing, stock status, lead time, and sourcing documentation summary.
- Confirm & Ship: Upon order confirmation, units are inspected, packaged, and dispatched with full QC documentation. Express and standard international shipping options available.
Replacement & Compatibility FAQ
Q: Can I use a 1785-KA as a direct replacement for the 1775-LX?
No. The 1785-KA is a communication adapter for the PLC-5 platform and is not a drop-in substitute for the 1775-LX, which is PLC-3 specific. The backplane interface, firmware, and connector pinout differ. If you are migrating from PLC-3 to PLC-5, contact Konmask for a full migration bill of materials.
Q: Is the 1775-LX compatible with ControlLogix or CompactLogix systems?
The 1775-LX is not natively compatible with ControlLogix or CompactLogix platforms. However, a DH+ communication module (such as the 1756-DHRIO) can be used as a functional equivalent bridge to connect legacy DH+ devices to a ControlLogix system. This is a common equivalent solution for system modernization projects.
Q: What is the best substitute for the 1775-LX if the original is no longer available?
For applications where a genuine 1775-LX cannot be sourced, the recommended substitute strategy is: (1) source a certified-refurbished OEM unit through Konmask, (2) evaluate a DH+ gateway module as a functional equivalent for network bridging, or (3) initiate a PLC-3 to PLC-5/ControlLogix migration. Konmask provides free technical consultation to help identify the most cost-effective equivalent or replacement path for your specific system.
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