LG 60LM7200 TV no responds to the IR remote, main board damaged?

I have an LG 60LM7200 TV which can be turned on, but it no longer responds to the IR remote. I changed the batteries and tried another LG TV remote, but it only responds to the POWER key. Also when using the TV's own keyboard, it responds only to the POWER key, none other keys. I suspect the main board's microcomputer might be damaged. The chassis number is LB22E or similar.

Anybody knows where can I find this board for sale in the US?