did that , no boot/chimeJust for testing, swap the BIOS/SPI ROM chip from another 3115 onto this board. If it chimes, you have either bad BIOS or dead/faulty chip.
If you DO get a chime/boot, then load up a new BIOS with the original/correct serial number, MLB and a clean ME region. PRAM on 1st start.
If you DON'T get a chime/boot, then you can eliminate BIOS/SPI ROM chip as the cause, and replace the original chip back on the board.