Looking at the wiring diagram I enclosed earlier you can see that the drum light is the first part in the circuit.
So I would say that your problem may be with the wiring going to the dryer, the line cord or the door switch.
The timer is not part of the lights circuit so I doubt this is the problem.
Try flipping the breaker off/on slowly a couple times, sometimes you can loose half the line without actually tripping the breaker.
If this does nothing, check the voltage at the plug
L1 to L2 should be 240 volts
L1 to Neutral and L2 to Neutral, both should be 120 volts.
L1 to Neutral runs the light and the motor.
Unplug the unit and check the wires at the terminal strip in the machine to make sure none are loose or burned out
Check the power at the terminal strip.
Be careful as 240 volts is lethal !!!