Compact RAR archive, roughly 397 KB, labelled LX6-MB-I with no brand or file type stated. The MB token likely means motherboard, but the device, revision and contents are not given, so open the archive to identify what is inside. If it is a schematic or boardview, confirm the code on the PCB matches before using it to follow power rails, find test points or isolate a short. If it is a firmware dump, save the existing chip contents with a programmer and check that the sizes agree before flashing.
The button opens the matching file on RM Schematics, or a source page if it is not catalogued there yet. The original attachment is from @cyberlanelectonik. Enginerys does not host this file.
How to open a .rar file
Compressed archive — the usual wrapper for a schematic + boardview pair or a BIOS + EC set.