Sony 770es intermittant problem

[reddish75]

Hi, my sony 770es has developed an intermittant problem where it will loose audio from both channels or sometimes just the right or left. When it comes back on there will be a cracking sound from the speakers.

I have visually checked all of the pcb's and cannot see any dry or cracked joints. I have also checked all transistors with a friends peak component checker and they all check out ok.

Is there anywhere else i should be concentrating on looking? The protection circuit prehaps?

service manual is downloaded here
Sony TAF-770-ES solid state amplifier

thanks
chris