technika lcd32-407B ?

i have a technika lcd32-407B lcd tv which was given to me.when its turned on it sometimes buzzs loudly from the speakers...no display...or no buzzing. sometimes when its turned on there seems to be a lot of hissing,low buzzing comeing from the power board which eventualy gos away....then on some occasions it dos start up after iv turned it on and of a lot of times.
all the capacitors look ok. iv checked the voltage on the leads that plug in the board on the right hand side under load and its fine....any help??