Macintosh Classic is the only Macintosh coming with OS in ROM – it can be booted by pressing CMD-OPT-X-O keys together and rebooting machine (try to do this in one person) – it is pretty cool!
Power Supply/Analog board
If your power supply gives no sign of life (meaning there is voltage on the primary winding of the transformer but not on the secondary), the first thing to replace is TDA4605-3 control IC for the power supply. It probably should be replaced together with accompanying capacitors, which may be the reason for failure.
Floppy Disk Drive
If the FDD is not reading the disks, inspect the distance between the upper head and the disk surface. If there is space, the heads have to be removed (together with the harness that is moved by the stepper motor) and it is possible to adjust the strength of a spring pulling the heads together from the bottom of the harness.
SCSI terminator (branded by Apple!)
A battery from 1991, that is not leaked at all! (although someone mounted it in a wrong direction)