Use a multimeter in continuity mode to find the common ground. This is your reference point for all voltage checks.
Version 1.3 often includes upgraded Zener diodes and thermal fuses to prevent overcurrent damage. Troubleshooting Without a Schematic bm5291 ver 13 schematic free
Sites like BadCaps or EEVblog often have users who have hand-traced these boards. Use a multimeter in continuity mode to find