Main Board Replacement

This guide covers replacing the main board on the Vision Miner 22IDEX V3 and V4 - both versions use the same board and the same procedure. The main board is the central controller of the machine: it runs the firmware from its microSD card, provides the network connection, and talks to the expansion board over the CAN bus. The replacement procedure is analogous to the Expansion Board Replacement - the board sits in the same electronics bay, mounts on four standoffs, and uses the same tools.

Tools and Materials

• Main Board
• PH2 Phillips screwdriver (for the 24V power terminal screws)
• 2 mm hex key (for the board mounting screws)
• Permanent marker (for labeling the connectors)
• Phone or camera (to photograph the wiring before disconnecting)

Confirming the Board Is Dead

The main board sits in the electronics bay above the expansion board. Both boards have power indicator LEDs - blue (24V), amber (12V), red (5V), green (3.3V) - and a DIAG status LED; on the main board it is next to the microSD slot. In normal operation both DIAG LEDs blink in sync, one second on, one second off. Before replacing the board, work through the Unresponsive Printer guide to confirm the main board is actually at fault - a board that shows no signs of life is rare, and in most cases the problem is elsewhere.

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Removing the Old Board

1. Power off. Turn the printer off and unplug the power cord. Wait at least 60 seconds for the capacitors to discharge.
2. Document the wiring. Photograph the board and label every connector with a marker so reassembly is unambiguous (the board is labeled next to each socket). The Wiring Schematic (V4, V3) is the backup reference.

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3. Disconnect all the cables from the board. Unplug every connector: the endstops, the servos, the temperature sensors, the motors, the fans, and everything else plugged into the board. Two cables deserve special attention so nothing gets missed:
   • the CAN bus cable with the RJ connector - it carries the communication between the main board and the expansion board;
   • the Ethernet adapter cable in the port on top of the board - it extends the Ethernet port to the outside of the printer, so the network cable plugs in from the printer side without opening the rear compartment.

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4. Disconnect the power. Unscrew the two screws securing the 24V power cables and free the cables.

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5. Remove the Wi-Fi module. The Wi-Fi module simply pulls off the board by hand - there are no cables or antenna to disconnect. Take it off and set it aside: it moves to the new board.

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6. Take out the microSD card. The card holds the machine configuration and moves to the new board as well.

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7. Remove the board. Unscrew the four screws holding the board on its standoffs with the 2 mm hex key and take the board out.

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Installing the New Board

1. Transfer the microSD card and the Wi-Fi module. Insert the card from the old board into the new one and press the Wi-Fi module onto its connector.

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2. Set the power jumper. Above the terminals where the 24V power line connects, there is a 3-pin contact with a 2-pin jumper on it. Move the jumper to the far right position so it bridges the right-most and center pins when you are facing the board directly.

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3. Mount the board. Seat the new board on the four standoffs and fasten it with the four screws using the 2 mm hex key.
4. Connect the power. Attach the 24V power cables with the two terminal screws.
5. Reconnect the peripherals. Plug every connector back into its socket, following your photos and labels. Reconnect the CAN bus cable and the Ethernet adapter cable in the top port. Double-check against the Wiring Schematic (V4, V3).

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Verification

1. Plug the printer in and power it on. The main board's DIAG LED next to the microSD slot should start blinking in sync with the expansion board's - one second on, one second off - and the Web Interface should become reachable.
2. Check the firmware versions. In the Web Interface, open Machine-Specific and compare the Duet 3 and Duet 3 Expansion versions - they must match. If they do not, update the main board: type M997 B0 into the command line at the top of the screen and press Enter - the board pulls the correct firmware from the SD card. See SD Card & Firmware Recovery if anything goes wrong.

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3. Do a full power cycle. After any firmware update, turn the printer off, unplug the power cord, wait a few seconds, and power it back on. Some subsystems only come fully alive after a complete restart.
4. Run the QC self-test. Go to Macros → System → Calibration → QC → Test 1 and work through the test sequence - it verifies the voltage, LEDs, heaters, fans, extruders, movement, endstops, filament sensors, and homing one by one. Any step can be skipped with Skip, but the more you test, the more confidence you have in the new board.

FAQ

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