Flashing custom firmware (MK4/S, MK3.9/S, MK3.5/S)

Relevant for:

MK4 MK3.9 MK3.5 MK4S MK3.9S MK3.5S

Last updated a month ago

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The Original Prusa MK4/S, MK3.9/S, and MK3.5/S are equipped with an xBuddy board.

In their factory state, our printers only accept official firmware. To flash any unofficial firmware to the printer, it is necessary to break the appendix on the xBuddy board.

Breaking the appendix on the mainboard of the Prusa MK4/S, MK3.9/S, and MK3.5/S is IRREVERSIBLE and leads to VOIDING OF THE WARRANTY ON ELECTRONIC PARTS OF THE PRINTER.
If you break the appendix, we disclaim any responsibility for any damage to the printer and/or its surroundings (e.g. in case of a fire).

Before attempting this procedure, carefully review the description and the photo below.

To break the appendix, open the electronics box and locate a safety seal on the xBuddy board, with an exclamation mark on it. Then, take a small flathead screwdriver or very thin sharp pliers and break off the thin middle part of the fuse.

Once the appendix is broken, flashing firmware can be done following the procedure in the dedicated article on firmware updating.

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