Power on blank screen no sound

Hi! I bought a lot of gameboys and theres one that is giving me some trouble. The power led turns on normally but there's no image display or sound. I tested the "top" half of the gameboy with another one and the LCD screen and speakers do work so I limited the problem to the motherboard side of the console. However I can't seem to further locate the problem, no signs or corrosion of damage on any of the components. Has anyone encountered this before, any hints on where to start lookin for damaged components?