Sounds like you are in the begining stages of vertical foldover. This is a problem where the vertical driver waveform is distorted due to a component failure causing the beam to not be driven all the way to the top of the screen. Usually there is enough overscan that you would not necessarily notice the picture being smaller than the crt. When this happens the horizontal scan lines, which have not decreased, are all displayed on top each other or as the condition worsens they invert. This causes the symptoms that you described. The solution I use is to replace all the electrolytic capacitors in the vertical drive circuit. There may only be one bad one but finding it will drive you nuts. They only cost dimes so we're not talking much money. Without a schematic you can usually be successful if you replace all the electrolytic caps around the vertical IC. If you are going to tackle this be careful. TVs are dangerous. Remember to unplug the set and discharge the crt High Voltage anode. Good luck.
Jun 20, 2006 |
JVC AV-27D302 27" TV