Sites like Laptop-Schematics or technician-led Telegram archives sometimes carry Foxconn OEM diagrams.

: Page 1 – Block diagram confirms 5VSB originates from the ATX connector. Step 2 (Multimeter) : 5VSB present at pin 9 of ATX. But Super I/O (ITE8718) shows no 3VSB. Step 3 (Follow the schematic) : Page 8 – 3VSB is generated by a linear regulator U30 (usually an LM1117). Input 5VSB, output 3VSB. Measured input = 0V. Step 4 (Trace back) : U30 input comes from a zero-ohm resistor R512. R512 was open (burnt). Replaced. Result : Board powered on. This diagnosis was impossible without the Rev 1.1 schematic.

No official manual will tell you that a cracked resistor at location (as shown on page 14 of the rev 1.1 schematic) is why your RAM slot B is dead. Only the schematic provides that level of detail.

Without the schematic, the power sequence is inferred from standard G41 requirements:

With the schematic in hand, here are three common issues for the H-IG41-UATX Rev 1.1 and how the schematic solves them.