Attached to this post are PDF's of the service manuals for some of the 68k-based PowerBooks. Enjoy :)
powerbook_100.pdf - PowerBook 100
powerbook_140.145.b.170.pdf - PowerBook 140, PowerBook 145, PowerBook 145B, PowerBook 170
powerbook_150.pdf - PowerBook 150
powerbook_160.165.180.pdf - PowerBook 160, PowerBook 165, PowerBook 180
powerbook_165c.180c.pdf - PowerBook 165c, PowerBook 180c
powerbook_190.5300.pdf - Macintosh PowerBook 190/66, 190cs/66, 5300/100, 5300cs/100, 5300c/100, and 5300ce/117
powerbook_500_series.pdf - PowerBook 520, PowerBook 520c, PowerBook 540, PowerBook 540c
powerbook_550c.pdf (Japan only) - Macintosh PowerBook 550c
powerbook_duo_dock.pdf - PowerBook Duo Dock, PowerBook Duo Dock II, PowerBook Duo Dock Plus
powerbook_duo_minidock.pdf - PowerBook Duo MiniDock