Sorry. Inverter is the usual cause. Did you install it yourself from an eBay purchase? A lot of those sold are not new, and used ones look new.
Who disassembled your screen to do the work?
We assume you also checked the ribbon cable carefully for cracks and crimps... as that would be the next most likely cause. If you did it yourself, inspect the cables for both under a bright light designed for that work.
Check all those sockets carefully, as a couple of them come loose.
Luckily it is new enough to have parts available.
Lenovo service would replace the system board under warranty... How hold is your R61?

 

raybay-don't see relevance of checking ribbon cable if no voltage from inverter-cable from MB is discrete/ not ribbon...R61 manuf. date 2/08, so not too old, thanks,greybeard