This is a very frustrating problem and there are quite a few possible causes for this failure to happen with the Xbox. You can spend hours on the internet looking for an answer to this issue.
However, thankfully there is one very simple solution that is often overlooked when this problem occurs and I am writing this tip so that anyone who has this issue can check this out as first step in resolving the problem before moving on to anything else.
On the actual cable that connects to the XBox there is a little HD switch right on the side of the connector. If this little switch is in the HD position and your TV is non HD you will end up with sound and no picture!!!
Therefore please check this cable (see picture below for exact location of the switch) to ensure that it is in the position that is correct for your TV set.
If this does not resolve your problem please work through the following steps.1) Reset the display resolution to its default settings. To do this;
2) If you still do not have a picture - disconnect the cable that is shown in the picture above and then also remove the power cord for a total of five seconds.
- Remove any discs from the disc tray.
- Turn off the console.
- Turn on the console.
(If you are using an Xbox 360 Wireless Controller, turn on the console by using the Xbox Guide button on the controller. Make sure that you use the player 1 controller when you do this.)
- As the console starts, press and hold the Y button, and then pull the right trigger at the same time.
- The Xbox will reset to default display settings and automatically restart the console.
3) Reconnect the cables - make sure they are securely seated - turn on the console and see if you have a picture.
4) This problem is sometimes associated with faulty cables or damage to the connectors for the cables that are on the console itself. If there is no evident damage to the connector on the console - replace the cables.
These are the main steps you can take to troubleshoot the sound but no picture problem. If these fail then there is an internal component failure
and your console will need to be returned for a service repair.
Please note: There are reports of people using a method known as the 'blanket' or 'towel method' whereby the console is wrapped in a cover and then it is forced to overheat in an effort to melt any solder in the circuit that may be causing a dry joint. I strongly recommend against using this so called 'blanket method'.This is due to the risks of fire hazard and the strong likelihood that you will end up causing even more damage to the components inside your console for something that is at best a temporary fix. If your console continues to have display problems after working through this troubleshoot have the unit checked by an authorised technician.