Schematics for the FIC PTB51 motherboard at revision R0.6, compressed as a RAR archive of about 1012 KB. PTB51 is a First International Computer board code, part of a family that includes similarly named PTB designs. Open it with 7-Zip or WinRAR and view the circuit pages to follow power sequencing, check rail voltages and identify components near a fault. Before using it, make sure the board silkscreen shows PTB51 and the R0.6 revision, as neighbouring variants differ.
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 @IT_SERVICE_WORLD. 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.