Ensure that the unit is receiving power. This means checking the power cable is securely in place and the power is switched on at the mains. You may also have to flip a tripped breaker if that is the reason no juice is flowing.
Check that the fan thermal switch reset if you find the unit has a tendency of shutting off. This is a guard against overheating and is not indicative of a serious problem. Restarting the unit should fix the issue.
Clean optical systems or replace the faulty lamp if the lighting is dim, despite high settings on the console. Also ensure the 220/110v switch is at a high setting.
Make sure the connector is securely attached to the body of the device and is not damaged in any way if you find that the remote does not work.
Ensure you are only using DMX cables if you suffer from a loss of signal. You should also keep DMX cables separated from power cables or black lights.