Thanks for the datasheet. I already had it with me, but thx anyway.
i seem to have solved the problem, it seems that the technics guys had put a .01mfd cap across each contact of the main power switch for contact suppression. one side of the switch was not functioning which caused the cap to charge through the main transformer leading to a LC circuit. cleaning the switch contacts did the trick. the dead left channel was a disconnented main speaker contact at the back.
thx for all ur help ;D