Sony HCD-J3MD Service Manual page 15

Forced Reset
The system microprocessor can be reset in the following procedure.
Use these procedure when the unit cannot be operated normally due to hung-up of the microprocessor, etc.
Use of the RESET switch is recommended when the machine cannot exit the REtry CASE DISPLAY mode or a machine does not operate
correctly after re-assembling.
Procedure :
Press the S901 ( RESET button of the back panel) on the MAIN board.
[MAIN BOARD] (Component Side)
S901
RESET button
15