Don't forget to brush and vacuum the device before starting a repair. Removing dust often helps to properly look at every part, and it's easier to work on a clean instrument.Fan blades usually build up hard dust and dirt. I clean them with isopropyl alcohol or some contact cleaner, and finish with some WD-40. The WD-40 has a "non-stick" quality if you let it dry. Contaminants (soda, beer, champagne... I have seen more than I have tasted) might be a giveaway, and require thorough cleaning. Cigarette smoke will betray itself on the outside by coloration and smell. It can cause malfunctions in digital gear, mainly where high frequencies are used.Many keyboard mechanisms are greased "for life". But this grease equally picks up dust and hair for life. If the keys are sticky or slow, get rid of the grease. I usually lubricate with either WD-40 (apply on separate parts and allow to dry before reassembly) or some silicone oil or grease.