my Black & Decker charger died and I have a transformer that I want to use to replace the dead one. The old one was 17 volts DC and charged at 240 ma. The replacement is rated 19 volts DC and testing it reads 29 volts DC output. I need to replace the resistor on the circuit board to reduce this to 240 ma out to charge the battery pack. How do I find the resistance value needed to get 240 ma charge from the 29 volts?

Ohms law says it will take 120.8333 of resistance.