Rowe cd100 AMP issue -

[bobandjudy2]

I have a Rowe CD100 jukebox that has just started to have a problem with static after about 3 years of use.  When I play a CD it is clear for a period of time and then static starts on speaker.  You can still hear the music for about 30 more seconds but the static gets loader until it is very hard to hear any music.  After another minute or so both the static and music fade to nothing.  This whole process usually starts between 30 seconds and 5 minutes after turning on the jukebox.

I suspected that one or more of the 4 main transistor amps was going out, so I replaced them all.  All fuses are ok and no signs of any heat on the preAmp or two main driver boards.  Any thoughts on what to check next?