Pissed off with motor, want to change

Did the ballast resistor get even a hint of water on it / near it ?
Those damned things like to POP when they're hot ( been run for a bit ) and water -- even in vapor or mist form -- gets on them / near them .

Take the ballast off and inspect its backside , looking for cracks . Hell , they're cheap enough ; just buy one anyhow and plug it in . If that doesn't solve your problem , it's not much money out of your pocket , and you'll have a spare around for when it does go bad .