Akai AT93 overheating psu problem

[kimon]

Greetings to all fellows.My tuner,an AKAI AT-93,bought secondhand some months ago,after a couple (or so) hours on power starts intermitten operation and some displays are flickering.I read in a post by Jean Paul,diyAudio moderator,that this spesific model suffers from a badly designed power supply section.In a form of experiment, I took the device off the rack and removed the upper cover.It worked well,without any sign of malfunction,for several hours.I noticed that three transistors (tr9,tr10 and tr11) on the power supply pcb become hot,even with the cover removed,so that when I barely touched their heatsinks I had to move my finger right away.Transistor type is 2SD1406 with a junction temperature 150 C.Replacing them with 250 C types is a sufficient solution or a poor remedy?Is there anybody dealing (dealt) with this problem?I would appreciate any given help.