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[例10]长虹C2588A彩电,自动关机,再开机后,故障重复出现。分析与检修:自动关机,说明行电路未工作。分析原因:一是保护电路动作,切断行激励信号;二是电源电路存在故障;三是行电路有元件热稳定性不良或虚焊类故障。因红灯亮,说明主电源工作正常,因此先查保护电路。自动关机后测量行电源电压115 V正常,行推动信号无输出,TA7698的(30)脚约1.5 V,说明保护电路动作而关机。TA7698的(30)脚外接过压保护和过流保护,在路测量VD472、VQ841均正常,测量C309充、放电正常。采取解除防护的方法:断开过压保护管VD472后,开机不再关机,重测VD472正、反向电阻均正常。试代
[Example 10] Changhong C2588A color TV, automatic shutdown, and then boot, the fault appears again. Analysis and Maintenance: Automatic shutdown, indicating that the circuit is not working. Analysis of reasons: First, to protect the circuit action, cut off the line incentive signal; second is the power supply circuit failure; third line circuit components have poor thermal stability or Weld fault. Because of the red light, indicating that the main power is working properly, so check the protection circuit. After the power is off, the line voltage of 115 V is normal. The output signal of the line is not output. The TA7698’s (30) pin is about 1.5 V, indicating that the protection circuit is shut down. TA7698’s (30) feet external over-voltage protection and over-current protection in the road measurement VD472, VQ841 are normal, measuring C309 charge and discharge normal. To take measures to lift the protection: Disconnect the overvoltage protection tube VD472, the boot is no longer shutdown, re-test VD472 positive and negative resistance are normal. Test generation