The cost to replace the bad part, after paying a technician to diagnose the 5 or 6 boards inside the TV, mostly always exceeds the cost of replacement. You can buy a 42" 4k TV from Walmart for $200. Anyone of those boards inside your current TV can cost $150-$400, plus the $100/hr shop fee with a minimum of 3hr fix.
Sorry, but bite the bullet and buy a really nice TV. 10 years was a good run, but it's time to retire it.