Repairing a B&K ST140

Trying to find answers to some transistor questions. I have the schematics from B&K but they contain some odd part numbers. Q2,3,5,6,7, all are "PN4889" digikey has no idea what they are. Any one out there have a clue? Are there any mods I might make to this thing before I seal it back up?

System: Rotel CD player; Adcom Pre Amp, Which I modified "Straight wire"; Adcom GFA555 for the low end; B&KST140 for the high/mid end; B&W 801 Series 2, BiWired; NAD tuner; Monster cable sprinkled around...

Any way thanks in advance for the help.

Don