Facing TV Problems? Ask a TV Technician.
The 12 blinks is the 'error code' from Panasonic. Your particular error code indicates that the H board has a problem.
The board itself will cost around $50 - You can purchase this from the link below if you like:
With a new board in hand, and a little bit of time, you may be able to replace this yourself. If you feel uncomfortable doing this, it should take a local repair tech about an hour's labor.