That clicking sound coming from your Hitachi Projection TV could indicate a problem with the set, especially if it's accompanied by other issues like the TV not coming on. However, if everything else is functioning normally, the clicking might be coming from the TV cabinet heating up and expanding or the speakers picking up sound interference.
Hunt around to find the source of the clicking sound. Put your ear as close as you can to the sound. If it appears to be coming from the speakers, press "Mute" on the remote control to see if the sound goes away. If the sound is coming from the back of the TV, listen to see if it's coming from the corners of the case or from the internal circuitry. If the sound is coming from the inside, it's more likely to be located near the place where the power cord attaches, but if the sound is coming from the case, it's more likely to be at the edges of the cabinet, where the screws hold the TV together.
Your Hitachi projection TV has an internal surge protector that switches off the power flow if an electrical surge is detected. Press the power button on the TV and wait for 30 seconds. Try to power on the TV again. If it won't turn on and it keeps making the clicking sound, unplug the TV from the outlet for 30 seconds. Plug it back in and power it on. The clicking sound should stop once you reset the internal surge protector. If the situation keeps happening, try replacing the external surge protector into which you plug your TV or use a different outlet in your house.
If you press the power button on your Hitachi Projection TV and it makes a clicking sound, but the TV doesn't turn on, then there's an issue with the power supply. Your TV takes the alternating current from the outlet and transforms it into a direct current flow for the projection system. It uses relays to connect the circuit and then pipes the electricity through capacitors which smooth out the flow of power. However, if a capacitor is malfunctioning or a fuse on the circuit has blown out, the relay will click, but power won't continue down the pipe. If you hear the clicking sound but the TV doesn't come on, you should contact Hitachi for help (hitachiserviceusa.com/Customer.asp).
The powerful lights in your Hitachi Projection TV produce heat that is dissipated through the cabinet and into the surrounding air. If the case is cold when the TV is turned on or if the lights heat up the case unevenly, it might make a clicking sound while everything warms up. If the clicking starts after you turn on the TV and stops after the set has been running for a while, it's probably just heat expansion causing the sound.
If the clicking sound goes away when you mute the Hitachi TV, the noise is being introduced through one of the audio inputs. Play video through each of the sources one at a time until you find the culprit. Start with your set-top box, if you have one, and play both standard-definition and high-definition channels. Check your DVD player, video game console and any other components that send audio to your TV speakers. Once you find the source, plug that component into a different audio input on the TV, like the front-mounted inputs under the screen. If the clicking goes away when you plug the component into a different input on the TV, contact Hitachi customer service, because the TV's audio input port is defective. If the clicking remains no matter where the component is connected to the TV, then switch the cables and use a different set. If the clicking is still present with new cables, you know the component is causing the issue. Contact the manufacturer for customer service.