Dish Network Corp. lost a record number of TV subscribers in the second quarter as programming blackouts and price increases drove customers to seek cheaper online alternatives, reviving industrywide concerns about “cord-cutting.” Dish shed 281,000 pay-TV customers in the quarter, compared with a loss of 81,000 a year earlier, according to a statement from the Englewood, Colorado-based company Thursday. That marks the biggest loss of TV subscribers in any quarter. The rate of monthly customer defections, or churn, rose to 1.96 percent from 1.71 percent a year earlier, Dish said in a separate filing.