Dead TV - Please Help
It is possible that there are failed components in the CRT bias circuits, or one of the scan circuits, or in the power supply, or in the high voltage section.
When any one of the areas fail, the set goes in to protect mode and biases off the CRT. If any of the other areas fail, the picture will also go black. In some models of TV sets, the sound is not critical of these areas that are mentioned here.
To fix this problem, proper troubleshooting of the set will be required. There are many components involved in the TV set that can cause failures to appear to be of this type.
You will have to have the set serviced by someone who is experienced and equiped to do TV service.