Video Connections
There are three primary video connections that are used when connecting the PlayStation 3 to your television. Composite connection runs the video signal through a cable signified by the color yellow and the audio runs through two cables marked by red and white denoting right and left channels respectively. Component still uses the red and white audio cables but separates the video into red, blue and green cables. HDMI is a high-definition cable that sends both audio and video from the PS3 to the HDTV.
Video Modes
You can adjust each connection type to various resolutions based on the maximum resolution of your television. To switch between the different connections requires changing the Video Output Settings under the Settings and then Display Settings. However, if the device is stuck on HDMI and you don't have an TV to connect it to, then you're not able to access this menu.
Reset Videos Modes
By default, the system retains the graphics settings in place at the last shutdown. To reset the video settings, put the device into standby mode. Flip the power switch on the back of the device off and then back on. Connect the device to your TV, and hold down the power button until the picture on the TV begins to flicker. This takes approximately 10 to 20 seconds. The logo appears on-screen after a few seconds, and then you can start playing again. Any themes settings will be reverted to default as well.
Other Troubleshooting
If resetting the video settings doesn't resolve your PS3 problems, use a different cable of the same type to connect the device to the TV. Alternatively, use a different connection method. If the problem continues, contact a professional to take a look at the system.