Fault:- Color distortion. Intermittent or permanent.
A small hit on the backside of the TV cabin will make it right, at least for a moment. On some others can’t. With some sets, color combination will come right after a few minutes after switch ON. On some others, at first the color will be all right, but after some time, all color balance will be out and will show irregular color combination.
Eventhough, there is many reasons for irregular color reproduction with CRT based televisions, the most common fault will be with loose soldering points at the Video Output Section. In most of the TVs, the video output section will be at its picture tube baseboard itself. Older TVs of Mitsubishi, have this section is assembled at main board itself, and only wires are connected to picture tube baseboard.
Take the first case. (A small hit on the backside of the cabinet, makes color and picture right, at least for a moment.
The fault is with loose soldering points on the video output section, assembled on the base card of the picture tube. As you know, proper mixing of the three primary colors, Red, Green and Blue, does all the color combination.
If any one among the primary color misses, you will get a picture with something strange to describe.
Take the first case. With a small hit on the back or side of the TV makes it right even for one moment or so.
The fault is with some loose soldering points itself. But, must check and detect the exact point of fault. As I said earlier, the fault is with video output stage itself, which is venerable to get loose soldering points. Most of the components at the video output stage, whether it is assembled on main board, or at the picture tube baseboard, should be checked for loose soldering points.
You will get the exact fault point, by a close look at this board itself. Look for any cracked soldering points. You may have to use a magnifying glass to get these solder cracks, as some of them will be microscopic. Just do, what we do in service field if the fault detected is with loose soldering. Just resolder all the soldering points on the base card board, including picture tube base card connections, by applying al little more solder to each solder points, without making any solder short in between adjacent solder terminals. If the fault was due to loose contact with this video output card, it will be all right by now. You can solder all these solder terminals with base card plugged in.
If the fault is not with this base card, you have to go further to chroma section circuits of the TV, and you must have knowledge and proper testing tools, schematic diagram of your TV set. Must have concentration and patience. Without patience, you can’t do any work in electronics repair.
