Dell inspiron 1540 power supply not working. Power is reaching from plug to the unit. Measured it with volt meter. However the led light in the unit is not showing so the problem must be in the unit? The unit is sealed so cannot b opened. End of story. Need a new one, but am in a remote part of West Africa where it won't be easy. Anything I might try in the faint hope of prompting it back to action?