Thousands of Brisbane racing fans have been left in the dark after a power failure at Eagle Farm Racecourse threatened to ruin their Melbourne Cup.

Screens were blank and bets were unable to be made after the power went out shortly after 1pm on Tuesday in a blackout that lasted until about 2.50pm - almost an hour after the Melbourne Cup was run and won..

Thousands of racing fans watched the great race on their mobile phones while scores more in general admission fled the track looking for the nearest venue with a TV screen.

The Brisbane Racing Club was expecting to have to deal with requests for compensation after a "couple of thousand" racegoers left while "more than 10,000" stuck it out.