Analysis and Repair: Based on the fault phenomenon analysis, it is determined that there is a fault in either the picture tube circuit or the video amplification output circuit. Measuring the cathode voltage of the picture tube, the three cathode voltages are all 0V. Adjusting the brightness knob shows no change in cathode voltage, indicating a fault in either the cathode power supply circuit or the video amplification circuit. Upon checking the video amplifier circuit, the c-electrode voltages of transistors Q505, Q508, and Q511 are all found to be 0V. A further check along the circuit reveals that the voltage at the other end of the current-limiting resistor R443 is 175V, which indicates that R443 (1Ω) has become open-circuited.
Source: Beijing Toshiba TV After-sales Service Phone Number [http://blog.tianya.cn/blogger/blog_main.asp?BlogID=3764604](http://blog.tianya.cn/blogger/blog_main.asp?BlogID=3764604).
Repair Method: Replacing R443 with a same-specification resistor (1Ω) resolves the fault. The audio function of the Toshiba TV works normally, but the raster is unusually bright.