The government deadline for installing home-end devices for a compulsory digital upgrade at five million cable TV households in four metros ended Wednesday.
But 9%, or about 500,000, homes are staring at a blackout as they haven't made the switch.
In Delhi, nearly 5% households are likely to face a blackout, while 17% households remain uncovered in Kolkata and 38% cable homes in Chennai may wake up to blank screens, government figures showed. Only Mumbai had achieved a 100% changeover.
In a nation where TV watching is a national pastime, an outage may escalate into a political showdown and add to the UPA government's worries. Political opposition in Maharashtra and West Bengal may prompt strikes by neighbourhood operators.
"We intend to move the Supreme Court," Anil Parab of Mumbai's Cable Operators' Distributors Association said.
And the move is being backed by the opposition Shiv Sena.
In Kolkata, chief minister Mamata Bannerjee has vowed to resist digitisation.
A supplier in Delhi said there was a shortage of imported set-top boxes.
"I am yet to get delivery of set-top boxes worth R10 lakh. It will take time," said HS Kohli, a stake-owner in Digicable, one of the five large firms that supply local cable distributors.
Low-income households used to cheap cable tariffs are the ones slowest to switch, which requires them to buy set-tops worth Rs 799, excluding taxes. The information and broadcasting ministry, however, said its ground teams were making good progress.
In December 2011, Parliament passed a Bill to digitise the cable television sector by 2014.
The Cable Television Networks (Regulation) Amendment Bill 2011 provides for compulsory digitisation, a move prompted by largescale under-reporting of subscribers by cable distributors, which ultimately hurts government revenue.