Solution: After soldering it with a soldering iron, the fault was eliminated.
Data source: Beijing Skyworth TV Repair http://blog.tianya.cn/blogger/blog_main.asp?BlogID=3687333.
Skyworth CTV-8298WF type TV, the screen shows a blue background raster.
Analysis and Maintenance: The normal blue background raster indicates that the main power supply, line scanning circuit, field scanning circuit, and image tube ancillary circuits are basically working properly. It is suspected that the fault may be caused by poor common channel or control circuit (i.e., CPU circuit). Measuring the voltage of each pin of the high-frequency head, it was found that the tuning voltage control pin (VT) voltage was 32V, and the tuning voltage did not change when pressing the channel selection button. Then measuring the voltage of pin 1 of the CPU (i.e., VT pin) showed 0V, and the voltage of pin 42 of the CPU (power supply pin) was also 0V, indicating that the CPU was not working. Measuring the output voltage of pin 3 of IC004 (LC7805) showed a normal 5V, thus judging the fault to be between the 5V power supply circuit and pin 42 of the CPU. Checking along the way, it was found that the copper foil at CN101 (key-controlled board socket) was broken.