Verticle lines appearing near top. Reminiscent of more extensive problem a few years ago that repair man said were related to electronic equipment used nearby such as vacuum cleaner. He fixed it with...
If the horizontal lines are red, green or blue or white, and are slanted about 15 degrees up going left to right, they are "vertical retrace" lines. These are caused by the beam current in the offending gun being left on while the vertical deflection is retracing from the bottom to the top on its way to start drawing the next frame. The usual cause is the CRT screen setting being too high (too bright), but (rarely) it could be something wrong with the vertical blanking circuit. Since it is dependent on vertical position, I would check the power supplies feeding the vertical deflection circuit and the CRT bias voltages, especially if they share the same filter capacitor.
If the lines are true horizontal, and colored similarly to the picture (sometimes alternately white and colored the same as program material), the top of picture is folded over itself because of over-voltage distortion ("clipping") in the vertical drive. In this case, reducing the height of the picture also reduces the fraction of the picture with the lines, and may eliminate it. If you are unable to get a full-height picture without the lines, then you should check the vertical deflection circuit for leaky capacitors (also check the power supply voltage going to it).
Several times I've observed bright white lines with random interruptions at the top of a picture supplied by the local cable company. These often occur on one or a few channels for a time (once or twice I've seen it on all channels), and go away after a while. This is a glitch in the cable service.
You have a zone of weird colors at the top of the screen. This is probably caused by magnetization of the shadow mask inside the front of the picture tube that is not being erased when the TV is first turned on. Check to see if somebody left a magnetized object on top of or above the TV (look behind the set also). If you find something remove it, turn off the TV, wait a few minutes, then turn it on again. (Explanation: the TV has an internal demagnetizing coil that operates only when you first turn it on. It uses a self-heating temperature-dependent part to gradually reduce the alternating current going through it to override and "fade out" any stray magnetism in the shadow mask.) If the internal demagnetizing (AKA degaussing) coil isn't strong enough, you'll need that "ghostbuster" gadget again. If you don't find an external magnetic source, the internal coil may have slipped out of place at the top of the picture tube and is too far away from the shadow mask, or something is wrong with the degaussing circuit.
If none of these cases match what you see, try a more detailed description of the lines and I'll give it another shot.
Nov 27, 2010 |
Sony Televison & Video