Hello,

http://www.chesscomputeruk.com/Mephi...ese_Board-.pdf
(Mephisto_Exclusive_-Saitek_Chinese_Board-.pdf)

See page 4 :

LED missing or turn on when it should not
1. Check if the corresponding LEDs are defective.
2. Check for no broken wiring connection between PCBs.
3. Check for short/open circuit on PCBs.
4. Check if U2 and U3 are functionally good.

Cordialy,

mychess