Fault phenomenon: Sometimes, only the lower half of the raster is visible, while the upper half shows a black screen. Analysis and repair: Upon checking with the cover open, it was found that pin ⑥ of the field output IC (TDA8172) was not connected to the base board solder hole, but instead touched the negative lead of D1503, causing intermittent raster faults. After re-soldering, the raster covered the full screen. However, the upper part of the raster showed scan lines and slight curling at the edges. The voltage on pin ⑥ of the IC was measured to be 1.5V (normal value should be -13V). As it was impossible to confirm the condition of the IC, the circuit was carefully analyzed and it was discovered that the peripheral circuit of this IC is the same as that of STV9379. After trying to replace it with STV9379 and turning on the machine, everything worked fine. But after using it for some time, when the machine heated up, distortion appeared in the lower part of the screen. Later, after installing TDA8172 and testing the machine, it returned to normal. This happened on a Changhong TV. In Changhong TVs, sometimes only the lower half of the raster is visible, while the upper half shows a black screen. Article source: Beijing Changhong TV after-sales service phone http://blog.tianya.cn/blogger/blog_main.asp?BlogID=3764634.