I have owned a TZ and repaired a few, PM me if you have any specfic questions. Main things to look out for in TZ are the function of the spiral magnets as well as the mini playfield (flipper magnets), the function of the gumball/clock as nino mentioned. The colour of the clock housing, if original, will give you a good indication how cooked the clock boards are. Make sure the ceramic ball is also present.There is a lot going on in a TZ so if your first pin then I suggest buying one fully working. There are many replacement parts available but will add up quickly in cost if most have to be replaced.
