In selling a controlling stake to Comcast Corp. in 2011, General Electric Co. began to unravel part of the legacy of former Chairman Jack Welch. In 1986, he had bought RCA and NBC to help his industrial conglomerate get a reliable source of cash while overseas manufacturing competition loomed.Under Comcast, NBC did better than expected during last summer's Olympics and began showing clear signs of a comeback, improving ratings after nearly sliding into irrelevancy over the previous decade. It had a new hit in "The Voice" and a consistent ratings leader in "Sunday Night Football" during the fall and early winter. By last fall, NBC could boast that it was drawing the most viewers in the 18-to-49-year-old demographic prized by advertisers for the first time in a decade. Overall, NBC still ranked behind CBS and ABC, but at least it was no longer bringing up the rear in fourth place, as had been the case for several years. With Tuesday's deal, Comcast would get full ownership. GE would end its ties with the network â¿¿ one that dates back to NBC's origins. Until RCA became the sole owner of NBC in 1932, GE owned the company along with RCA and Westinghouse.