Samsung Yh-920?

Hi,

I have a Samsung yh-920 gs my problem is the item will not power up. How can i fix this, I know that the hard disk is fine and the battery is fine because i have got it to switch on before by pressing the front and back of the unit together hard i know the switch works and LCD, its like there must be a loose connection somewhere i have taken the unit apart and looked with a magnafying glass and i cannot see anything. When it switches on the unit works fine e.g. plays tunes all buttons and menus are working. Does any body know what the fault is or how to fix it, any info on this would be very helpful.

Thanks.