I found that the charging status LED on the newer bricks will work properly on the older books. My ibook G3 500 shipped with a yo-yo adaptor, but the newer one works fine. So I would think it would work on a PB G3 as well
PB G4 15" 1.2ghz - Pismo G3 400 mhz - iBook G3 500 "Jukebox"
"SawSmurf" G4 500 - Quicksilver G4 Dual 1ghz modding...