Hi, did you check the battery see if any voltage? if it has voltage then you don't have to switch board, several ways to boot, hold the home button and connect to itune, it should detect it after 10 seconds, if not, connect to itune anyway, then hold down the power & home for 10 seconds and release the power button but still hold the home button, it should detect by itune about 18 seconds or just hold down power & home button for 15 seconds the press the power button for 2 seconds, it should show the apple logo in process, this will reset.
BTW, you can not jump charge the battery when it's connected to the board, you'll have to disconnect it from the board and check the voltage or charge it.
Regards