Search for the brand name of the device the BM5291 is inside (e.g., a specific brand of monitor or inverter) rather than just the board number.
Version 1.3 boards are often lead-free; check for brittle or cracked solder around high-heat components like inductors. bm5291 ver 13 schematic free
Use a multimeter in continuity mode to find the common ground. This is your reference point for all voltage checks. Search for the brand name of the device
Look for the switching transistors (often TO-220 or surface-mount packages) which are the most common points of failure. bm5291 ver 13 schematic free
If you cannot find a free PDF download of the exact Ver 1.3 schematic, use these professional tracing techniques to map the board: