Siemens 1790L811A Terminal / I/O Board – MM430/MM440

What Is the 1790L811A I/O Board?

The Siemens 1790L811A is the terminal and I/O interface board for MICROMASTER 430 and MM440 drives (also compatible with MM410/MM420). It provides the physical connection and signal interface between the drive and external control systems — handling digital I/O (DI/DO), analog I/O (AI/AO), start/stop commands, frequency setpoints, and status feedback. This board is supplied as new original stock, suitable for maintenance and repair where the existing terminal board is damaged or an IO board identification fault is present.

Important Compatibility Note: The 1790L811A is the I/O board only. It is not the main control (CPU) board. MM430 and MM440 I/O boards are interchangeable regardless of power rating, but the control/CPU boards and BOP panels are not interchangeable between the two series–. Confirm the existing board marking before ordering.

Technical Specifications

When to Replace the 1790L811A I/O Board

Typical conditions that point to the I/O / terminal board include:

• F0054 (Wrong IO Board) — the drive detects an incorrect I/O board or no valid ID data from the board. The fault description explicitly includes “Wrong IO board is connected” and “No ID detected on IO board”.
• Digital or analog I/O signal abnormalities — inputs not registering, outputs not switching, or analog setpoints/feedback reading inaccurately, after confirming wiring and parameter settings.
• Relay output failure — relay outputs not switching as expected, confirmed by checking r0747 status and the relevant P073x parameter assignments.
• Intermittent connection issues — MM430/MM440 control and I/O boards connect via a multi-pin header; long-term operation can cause poor contact at the interface.

These are diagnostic reference points, not a replacement guarantee. Confirm the drive’s parameter set and wiring condition before concluding the I/O board is the root cause.

Ordering & Verification

Before ordering, confirm the following:

• Drive series — MM430 or MM440. The I/O board is interchangeable between them regardless of power rating, but the CPU board is not–.
• Existing board marking — confirm the original board reads 1790L811A or one of the alternate part numbers above.
• Terminal layout — check the terminal designations on the existing board against the replacement to ensure the signal assignments match your wiring.
• If any point is unclear, send a photo of the original board label and terminal arrangement for review before purchase.

Frequently Asked Questions

Is the 1790L811A compatible with both MM430 and MM440?

Yes. The I/O board is interchangeable between MM430 and MM440 regardless of power rating. However, the main control (CPU) board and BOP panel are not interchangeable between these series–.

Is this the main control board?

No. The 1790L811A is the terminal / I/O interface board. It handles external signal connections, not the drive’s core vector control or firmware.

What are the alternate part numbers for 1790L811A?

A5E02490424, A5E00684817, and A5E00224211 are listed as alternate/equivalent part numbers