LG TV, model number 55LF6090-UB, repair advice. All three HDMI ports have separated from the main board. Need assistance identifying a correct replacement board.

SOURCE: replace main board on LG 42LC7D-UB

Try this place, http://www.shopjimmy.com/catalogsearch/result/index/?q=42lc7d-ub&p=2

I the best place I know of to get parts at a good price.
There are a couple of boards that have different part numbers. You'll have to match the part# with yours. It maybe out of stock, but click on it. Then click on "find other products with this part number". Then all the main boards show up with that part number. A couple of them should be should be in stock.

SOURCE: TV repair person told me

Even if you buy the parts you may get sticker shock!!! Why did it need a power supply and another board. Will your set come on? I may be able to give you part numbers but you need to be specific about which other board you think you need such as X Y signal board or power supply Some single circuit boards for some sets are as high as 600 bucks hope not for you

SOURCE: replace main board on LG 42LC7D-UB

not sure what you're referring to as a "main board", but heres the LCD Control Board for the TV

http://cgi.ebay.com/LG-42LC7D-UB-LCD-CONTROL-BOARD-6870C-0119A_W0QQitemZ150277759127QQcmdZViewItem

SOURCE: Serial number of ASUS motherboard

its imprinted in the board itself in SMALL letters need a magnifying glass and a flashlight to see then there either near the center or the outside edge

SOURCE: I have a non-functional Sharp LC-32D62U (32") TV.

It would be possible if you can go into service menu and write all settings and implement with the new board by going back in and changing what you wrote down.