### Analysis and Repair:
The power supply rectifier voltage (310V) was checked and found to be normal, but there was no main voltage output of 140V. A dummy load in the form of a 100W/220V light bulb was connected after R487 at the main voltage output, but the main voltage still showed no 140V output. It was estimated that the issue could be with the power supply itself or the protection circuit. After desoldering resistor R420 in the protection circuit, the 140V voltage output was measured and found to be normal, indicating that the fault lies in the protection circuit. During the moment of startup, the voltage on pin 1 of XS2011 was checked and found to have no change, while the reset voltage (+5V) on pin 30 had a low-level change. When checking pins 24 and 25, no oscillation waveform output was detected, which revealed a problem with the external crystal oscillator (4MHz) of the CPU.
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### Handling Method:
After replacing the faulty 4MHz crystal oscillator, the fault was resolved.
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### Beijing Konka TV Repair Center: Case Study for T2987B Type TV Maintenance
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### Article Source:
Beijing Konka TV Repair - [http://blog.tianya.cn/blogger/blog_main.asp?BlogID=3761213](http://blog.tianya.cn/blogger/blog_main.asp?BlogID=3761213)
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### Fault Symptoms:
For the Konka T2987B type television, when powered on, there is no image, no raster, and no audio.