sony trinitron KV-21STR2 blown q604 and q603

[denver]

hi there, im new on this forum, can anyone tell me and help me work for the power supply of sony trinitron model KV-21STR2? the problem is the blown transistor labeled c4833 for q603 and q604, what is the cause of blown transistor? and how can i trace the faulty components, and the fuse never blown only the transistor blown. any suggestion, pls help me...

tnx in advance.......