3v3 Mod

Break trace on bottom side of board to remove 5V supply . This floats the 5V header pin. Install a jumper to connect the old 5V header pin to the 3.3V header pin next to it.

3.3V Modified CH341A

Break trace to disconnect 5V supply

Closeup of broken trace

Fit jumper to bridge 3.3V supply to the 5V pin which has been disconnected from 5V supply

Reference Info

Johannes' Blog
Pigoo BBS Discussion with Pictures - 1
Pigoo BBS Discussion with Pictures - 2