No boot. my pc no longer boots after changing the case. i have tried removing the board and

Question

my pc no longer boots after changing the case. i have tried removing the board and powering up with only the power supply , ram and board still no boot or beeps. i do get 3 beeps if no ram is installed. i aslo tried removing the bios battery for over 20min and replacing.the system worked fine when in the old case.