Not only is the Macintosh Classic prone to leaky surface mount electrolytic capacitors, it’s also prone to battery damage. The particular brand of 1/2 AA PRAM batteries used in the Classic have a tendency to explode electrolyte all over the logic board, in some cases causing irreparable damage. If you have a Mac Classic and you’re not sure when the battery was last changed, do it NOW! And of course, get it recapped at the same time.
The Mac Classic analog board recapping guide can be found here.