Company officials said the device performed without problem during January's Sugar Bowl and other earlier events.
They said the device has been removed and replacement equipment will be installed.
The power failure cut lights to about half of the stadium for 34 minutes Sunday night, halting play in the championship game in which the Baltimore Ravens triumphed over the San Francisco 49ers.
Officials of Entergy and the company that manages the stadium for the state had said they believed the problem originated in the switching gear, which is housed in a building known as "the vault" near the stadium. The Superdome has a direct line feeding from a nearby Entergy power substation. Once the line reaches the vault, it splits into two cables that then go into the Superdome.
The FBI had ruled out cyberterrorism as a cause.
The announcement came as Entergy officials prepared to go before a committee of the City Council on Friday for questions about the outage. The council is the regulatory body for the company.
SMG and Entergy announced earlier this week that they had been unable to find a specific cause for the outage and would hire an independent consultant. It wasn't immediately clear whether they would go through with the hiring.
The electrical equipment had been replaced after stadium manager's expressed concerns the Superdome might be vulnerable to a power failure like the one that struck Candlestick Park during a 49ers Monday Night Football game in 2011.
City officials had worried that the outage might harm New Orleans' chances of getting another Super Bowl.
But NFL Commissioner Roger Goodell said the league plans to keep New Orleans in its Super Bowl plans. Mayor Mitch Landrieu said the city intends to bid for the NFL's 2018 championship game.