It says buzz and suddenly turns off just after turning on?

Sounds like another flavour of the dreaded NVIDIA issue. If you have an Apple Service Provider within reach, take it there. They check it for a specific error code using a trick program on an external harddrive (not available to mere humans). If it spits out the correct error code - bingo, the'll replace the logicboard up til 4 years after purchase, no questions asked.

If not, i reanimated quite a lot of these machines by giving the LB a good and thorough clean with 99% rubbing alcohol and dried them carefully at ca. 100 degreee centigrade wrapped in aluminium foil. If you do that kind of "voodoo mac repair" remember to take out the ram and the two little plastic pads on the north side of the LB. Dust on the board, especially in connection with humidity can do all sort of weird things with your machine.