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一台牡丹35HB—1型35cm黑白电视机,出现灵敏度下降的故障,只能收到当地强信号电视节目,图像质量也不佳,弱信号电视节目一点儿也收不到。观察荧光屏发现高频头旋至无节目频道时,屏幕上净光,无任何噪波点。测量高放AGC为2V,偏低。正常应为3V左右。调整R_(207)(5.1k)至20kΩ,AGC电压达到2.4V.断开R_(207),AGC电压仍然调不到3V,接收效果也无明显改善。测量V_(201)
A Peony 35HB-1 35cm black and white TV, the sensitivity of the decline in failure, can only receive local strong signal television programs, the image quality is not good, weak signal television programs are not received. Observation screen found high-frequency monophonic headroom to program-free channels, the screen net, no noise point. High-measurement AGC 2V, low. Normal should be about 3V. Adjust R_ (207) (5.1k) to 20kΩ and AGC voltage to 2.4V. When R_ (207) is off, the AGC voltage is still lower than 3V, and the receiving effect is not significantly improved. Measure V_ (201)