Here is diagram of Nokia N82 Power Switch ways, that explains show ON/OFF switch ways, helpful to reapir Power switch with jumpers if prints are broken/Damaged.
Problem: Nokia N91 speaker not working You can not hear other person while making a call Solution: Here is full speaker ways for Nokia N91. Observe carefully and make jumpers to solve the problem
Problem: White/ Blank Display Solution: Its better to change Display Filtersm (IC), In Case new Ic not available, remove red marked ICs and make jumpers as shown in picture below.