I don't have the schematic, but we took one apart when it failed.
We found that the component that failed was U1 (see pic) where it burned up on the board, when it fails, it also kills the diodes on the board (D14 & D14).
The components are very cheap to replace, the issue is desoldering them off the board. The PCB has a very, very thick copper backing, so it's practically impossible to get component U1 off the board.