Analysis and Handling: The fault symptom indicates a short circuit issue in the switch-mode power supply or the line output circuit of the device. Upon checking the switch-mode power supply circuit, it was found that the +115V voltage momentarily reached +20V at startup, then immediately dropped to 0V. This shows that the switch-mode regulated power supply has entered protection mode. Further inspection revealed that the base voltage of the protection control transistor Q804 was 0.7V, clearly indicating that the protection circuit had been activated. After checking, transistors Q804, Q826, and Q827 were all found to be intact. However, the emitter voltage of the phototransistor in optocoupler D836 increased momentarily at startup and then dropped to 0V, leading to the suspicion that D836 might be faulty. A new component of the same model was used to replace D836, and after powering on for testing, the fault in the color TV was resolved.
**Source**: Beijing Philips TV Repair Center - http://blog.tianya.cn/blogger/blog_main.asp?BlogID=3761179
**Fault Phenomenon**: Upon turning on the TV, there is no raster, no image, and no sound (a triple-fault condition). This issue was addressed by the Beijing Philips TV Repair Center.
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### Translation Explanation:
- "光栅" = Raster (referring to the scanning pattern on the screen)
- "伴音" = Sound/Audio accompaniment
- "三无故障" = Triple-fault condition (no raster, no image, no sound)
- "开关电源" = Switch-mode power supply
- "行输出电路" = Line output circuit
- "保护" = Protection mode/Protection circuit