Here is a basic outline of a Preventive Maintetance for your Slit Lamp:
Slit Lamp
Check all operations, mechanical, electrical & optical.
Ensure that bearing tube/ rollers operate correctly.
Check & adjust elevation and swivel locks.
Check for collimation of stereo microscope body.
Check operation & collimation of mag changer.
Check condition of lamp socket & housing.
Check operation & condition of power supply and all wiring.
Check alignment of Applanation Tonometer.
Check table levelness.
Check Hruby lens.
Check & adjust slit & filter and aperture operations.
Clean all surfaces.