Replacing the Form 4L HDMI cable

The HDMI cable connects the Light Processing Unit (LPU) to the printer’s motherboard. A damaged HDMI cable may prevent the printer from printing properly and cause errors related to the LPU.

Use this guide to replace the Form 4L HDMI cable.

Estimated time: 30 minutes

Overview: Prepare the Form 4L and a dust-free workspace for replacing the HDMI cable.

Step 1: Remove the build platform

Remove the build platform first to avoid dripping resin onto the optical surfaces.

Step 2: Remove the resin cartridges

Remove the resin cartridges and close the vent caps to prevent resin from dripping off of the bite valve and into the printer.

Step 3: Remove and store the resin tank and mixer

Unlatch the mixer and resin tank. Remove the resin tank and cover it with its lid. Set the tank aside on a clean, flat surface.

Step 4: Prepare the workspace

Clear a workspace around your printer. Ensure that the workspace is well-ventilated and free of dust.

Step 5: Clean the printer

Open the printer cover and clean any resin pooled on and around the LPU with paper towels. Dampen the paper towels with isopropyl alcohol if necessary to fully remove the resin.

Step 6: Unplug the printer

Disconnect the power cable before continuing with maintenance. Do not perform maintenance on the printer while it is connected to power. Wait five minutes after disconnecting the printer from power before proceeding.

Overview: Remove the side panels to access the touchscreen assembly and HDMI cable.

Step 1: Remove the mesh filter

Remove the mesh filter from the right side of the printer. Set the filter aside.

Step 2: Remove the lower right panel screws

Use a 2.5 mm hex driver to remove the four screws securing the lower right panel to the printer. Set the right panel and the screws aside.

Step 3: Remove the lower left panel screws

Use a 2.5 mm hex driver to remove the four screws securing the lower left panel to the printer. Set the left panel and the screws aside.

Overview: Remove the front panel to access the touchscreen assembly and HDMI cable.

Step 1: Remove the left front panel retention screws

Use a 2.5 mm hex driver to remove the three screws securing the left side of the front panel to the printer. Set the screws aside.

Step 2: Remove the right front panel retention screws

• Use a 2.5 mm hex driver to remove the countersunk screw securing the upper part of the front panel to the printer.
• Use a 3 mm hex driver to remove the screw securing the lower part of the front panel to the printer.

Set the screws aside.

Step 3: Position the printer

With a second person, position the Form 4L near the front edge of the workspace to access the bottom screws.

Step 4: Remove the bottom front panel retention screws

Use a 1.5 mm hex driver to remove the two screws securing the front panel to the bottom of the printer.

Step 5: Reposition the printer

With a second person, position the Form 4L so that there is at least 6 inches (150 mm) of workspace in front of the printer.

Step 6: Remove the front panel

Grip the front panel by its bottom corners. Carefully pull the front panel towards you. Rotate the front panel until its back surface is visible. Do not pull away from the printer as the touchscreen ribbon cable is still connected. Lay the front panel with the glass face down on a clean, level surface.

Overview: Loosen the LPU housing screws and remove the HDMI cable.

Step 1: Loosen the LPU housing screws

Open the printer cover. Use a 3 mm hex driver to loosen the eight captive hex screws in the LPU housing.

Step 2: Unplug the HDMI cable

Carefully lift the LPU and tilt it so that the bottom faces you. Locate the LPU’s HDMI cable. Squeeze the plastic retaining clip and unplug the HDMI cable from the LPU.

Step 3: Disconnect the tank heater cables

On both sides of the printer, the heater cables are oriented with the clip facing outwards. Release the tank heater cables by squeezing the tab on the connectors and pulling directly away from the LPU. Do not pull on the cable itself.

Step 4: Remove the LPU

Remove the LPU from the printer and set it aside.

Step 5: Thread the HDMI cable through the printer chassis

Gently thread the HDMI cable through the slot in the printer chassis. Thread the HDMI cable through the slots in the chassis behind the mixer belt and through the central slot in the printer chassis to remove it. Take care not to dislodge the mixer belt. Set the HDMI cable aside for disposal with electronic waste.

Overview: Install the replacement HDMI cable.

Step 1: Thread the HDMI cable through the printer chassis

Starting at the bottom of the printer, thread the HDMI cable through the central slot in the printer chassis. Route the HDMI cable behind the mixer belt and up through the slot in the printer chassis to the LPU. Take care not to dislodge the mixer belt.

Step 2: Connect the tank heater cables

Position the LPU so the cable connectors are oriented towards the front of the printer. Plug the left and right tank heater cables into the connectors on the LPU. The plastic tab should click into place to secure the cable.

Step 3: Connect the HDMI cable

Plug the HDMI cable into the port on the LPU. Ensure that the two prongs on the plastic retaining clip snap into place.

Step 4: Mount the LPU

Ensure that the optical cavity and LPU are free from dust and debris. Place the LPU onto the optical cavity and align the screw holes.

Step 5: Thread the housing screws

Use a 3 mm hex driver to loosely thread the eight captive hex screws in the LPU housing.

Step 6: Secure the LPU

Once all screws are loosely threaded, tighten the screws in a diagonal pattern as shown above. The screws should be secure but not overtightened. To avoid overtightening, grip the short end of the hex driver.

Overview: After replacing the HDMI cable, reconnect and secure the touchscreen assembly.

Step 1: Position the front panel for installation

Position the front panel at an angle to the printer. Make sure that the sheet metal tabs are positioned outside of the printer frame and that they align with the screw holes on the printer. Take care not to crush or fold the new touchscreen ribbon cable.

Step 2: Mount the front panel

Mount the front panel onto the printer frame. Ensure the two tabs on the bottom of the front panel slide the corresponding slots in the printer frame.

Step 3: Secure the right front panel retention screws

• Thread the 2.5 mm countersunk screw into the upper screw hole in the printer frame. Using a 2.5 mm hex driver, tighten the screw until finger tight.
• Thread the 3 mm screw into the lower screw hole in the printer frame. Using a 3 mm hex driver, tighten the screw until finger tight.

Step 4: Secure the left front panel retention screws

Thread one screw into each of the three screw holes in the printer frame. Using a 3 mm hex driver, tighten the screws until finger tight.

Step 5: Position the printer

With a second person, position the Form 4L near the front edge of the workspace to access the bottom screws.

Step 6: Secure the bottom front panel retention screws

Using a 1.5 mm hex driver, secure the bottom front panel retention screws to the printer. Tighten the screws until finger tight.

Overview: After performing any other maintenance procedures, reinstall and secure the side panels.

Step 1: Align the left side panel with the printer

Lift the left side panel and align it with the left side of the printer.

Step 2: Secure the left side panel

Thread the four 2.5 mm screws into the screw holes on the left side of the printer. Using a 2.5 mm hex driver, tighten the screws until snug.

Step, 3: Align the right side panel with the printer

Lift the right side panel and align it with the right side of the printer.

Step 4: Secure the right side panel

Thread the four 2.5 mm screws into the screw holes on the right side of the printer. Using a 2.5 mm hex driver, tighten the screws until snug.

Step 5: Reattach the mesh filter

Vacuum the mesh filter until it is free from debris. If the mesh filter cannot be cleaned, replace it. Reattach the mesh filter to the printer, ensuring that it is aligned with the air intake vents.

Overview: After installing the replacement HDMI cable, power on the printer and perform final checks.

Step 1: Power on the printer

Close the printer cover and connect the power cable to the printer and the power supply. Turn on the switch at the back of the printer. The printer initializes.

Step 2: Align the build platform

On the touchscreen, tap Settings > Tools > Align build platform. Follow the on-screen instructions.

Step 3: Inspect the optics

On the touchscreen, tap Settings > Tools > Inspect optics. Follow the on-screen instructions to ensure the Backlight Unit and LPU are functioning normally.

Step 4: Run a test print

Insert any missing consumables and upload and start a print. Check that the print starts normally and the parts print successfully. Contact Formlabs Support or your authorized reseller to share the results of the procedure.