All seemed lost for Bradford on Tuesday night when Northampton skipper skipper Kelvin Langmead fired visitors into a 3-2 lead in the second period of extra time, but defender Carl McHugh equalised with seconds remaining to set up a penalty shoot-out, which the home side won 4-2 - their third spot-kick victory this term.
On this occasion, Bantams top scorer Nahki Wells was thwarted by Shane Higgs, but failures from Danny East and Langmead left Ricky Ravenhill to complete the triumph from his side's final penalty.
The home side went in front after 35 minutes when James Hanson laid the ball into the path of the unmarked Will Atkinson, who scored with an angled left-footed shot from eight yards, but the visitors equalised two minutes before half-time as Bradford captain Ravenhill was judged to have brought down Ishmel Demontagnac and Demontagnac scored from the spot.
The second half was deadlocked until left-back Joe Widdowson handled substitute Adam Baker's goal bound shot and Wells stepped up to score from 12 yards.
However, when Bradford left back James Meredith failed to cut out a pass from visiting substitute Adebayo Akinfenwa in the third minute of stoppage time, Clive Platt took advantage to score with a low right-footed shot into the far corner to send the tie into extra time.