You have a short to ground when the motor is hooked up. This presumes that the motor is hooked up correctly. Before powering up the boombox, find and fix the short first or you could blow the resistor again. With the POS of the motor disconnected, and the neg still connected to ground, check the resistance. Then with the motor POS disconnected, check the resistor ohms to ground. Resistance should be high or infinity. If the ohms slowly rise to infinity, that is normal since it's coupled to ground through a capacitor. If all that checks out, reconnect the POS of the motor and recheck the resistance from resistor to ground. One end should read same as reading from motor pos to ground. Other end should be same + approx 5.6 ohms. Also, check to verify that the capacitor is not shorted. If it is, then replace it.