My Latitude E6540 has the same problem. Few MOSFETs kaput. If repair at Digital Mall, need about 250. If replace the entire motherboard, need about 350-450 from AliExpress.

In the end, I chose to repair it at Digital Mall instead as I couldn't wait 1 month for the new motherboard. Since the repair, it worked well for almost 2 years now. I even upgraded the LCD to IPS and maxed out the drives to 3 and RAM.