LiftMaster K76-34728 EMI Board with AC Switch and 120V Receptacles — Compatible CSL24 / CSW24 Operators

The LiftMaster K76-34728 is the EMI-board service assembly identified in supported CSL24 and CSW24 gate-operator repair drawings. The manufacturer describes it with 120V receptacles and an AC power switch, distinguishing it from the main logic board, expansion board and reset switch. Select the assembly by the exact operator diagram and installed supply arrangement. This is a mains-side service component; the operator’s 24V motor designation does not mean every circuit inside the enclosure operates at 24 volts.

Compatibility — Models, Versions and Exclusions

Identify the Mains-Side Fault Before Ordering Electronics

An operator that does not receive AC power needs diagnosis of the incoming supply, switch, wiring and related components. A new EMI assembly will not correct an upstream electrical fault or damaged field wiring. Have qualified personnel establish which component has failed and confirm the correct service part before ordering.

The operator may still contain stored energy or a connected battery supply when AC is switched off. Follow the model-specific isolation procedure for every power source before working inside. When installing the replacement, preserve the intended grounding, mounting and wire routing. Do not repurpose the receptacles or change supply voltage based on the appearance of the assembly.

Specifications and Product Identification

Before Ordering

• Record the operator model and installed supply configuration.
• Match K76-34728 in the applicable repair diagram.
• Inspect the AC switch, receptacles, wiring and upstream supply.
• Confirm the current service package and all required power-isolation steps.

Package Contents and Separate Requirements

The manufacturer diagram identifies the EMI board with 120V receptacles and AC power switch. Confirm the current supplier assembly and any included mounting or connection pieces. The transformer, rectifier, batteries, logic board, reset switch and complete electrical enclosure are separate components unless explicitly included in the offer. Use the parts drawing to identify relationships without assuming a full electrical-box replacement is supplied.

Safety Warnings — Read Before Installation or Service

• WARNING: This assembly involves hazardous AC voltage. Installation and electrical diagnosis require qualified personnel familiar with the gate operator.
• Disconnect and secure every applicable power source, including batteries and solar where fitted, before service. An AC switch alone may not isolate the complete operator.
• Preserve grounding and the documented electrical configuration. Do not bypass damaged switches, protective components or wiring to restore operation.
• Restore covers and verify normal power operation, travel, reversal and all required protection devices before returning the entrance to use.

Related Products and Important Differences

• K41-0391-000 MAXUM EMI board — a different platform-specific assembly; compare exact part numbers, not an interchangeable substitute.
• LMRRUL monitored photo eye — a separate protection device for approved operators; an electrical repair must preserve the complete safety system.

Frequently Asked Questions

Is this the main control board?

No. It is the EMI and AC-switch/receptacle assembly identified separately in the repair drawing.

Does a 24V operator contain only low voltage?

No. The documented operator includes mains-side components and 120V receptacles as well as its DC drive system.

Can the MAXUM EMI board replace it?

No interchangeability is established. MAXUM is a different platform with its own service references.

Does turning off AC make the entire gate electrically isolated?

Not necessarily. Disconnect all applicable sources according to the operator’s service instructions, including backup power.

Need Help Confirming the Right Product?

Contact Garage-DoorParts.com before ordering. Send the full equipment model, readable part labels and photographs of the installed assembly. Include the dimensions, electrical configuration or accessory details relevant to your project so the listing can be checked against the actual installation.