the board overheat because of low voltage?
and it work fine for a month. Then it fail to function
Quoteand it work fine for a month. Then it fail to functionYes but then it should not have functioned in the first place.Does it work if you plug it into the USB.
The other thing it could be that you applied inputs greater than 0.5V above the power pin, as that was probably only at 3.5V a 5V input could kill the board.
using power adapter label as 5V. Kill the board?
You mean a wall-wart type? Is it 5VAC or 5VDC?
yes(I used my modem power adapter), 5VDC