TCL“王牌”9228型彩电常见故障的分析与检修(二)

• 作 者: 李其佳
• 出 处: 家电检修技术
• 发表日期: 1997年08期
• 关键词: TCL 调谐器 自动增益控制 混频级 音频信号 插头座 脚电压 小信号处理 信号流程 接收灵敏度

二、光栅正常,图像淡薄图像淡薄的原因在于整机接收灵敏度降低,涉及的范围较广,但可以根据以下两种情形来区别故障的大致部位: (1)如果画面“雪花”点多面对比度弱、图像淡薄,问题出自天线馈线、插件和高频调谐器内高放级、高放AGC等高频系统。 (2)如果画面无“雪花”(或稀少)而对比度弱、图像淡薄,问题出自高频调谐器中混频级、图像中放级及自动增益控制(AGC)电路。对于情形(l),应先检查天线馈线,插头座是否接

Second, the grating normal, light image The reason for the weak image is the lower receiver sensitivity, involving a wide range, but according to the following two situations to distinguish the approximate location of the fault: (1) If the screen “snowflakes” point multi-faceted contrast is weak , The image is light, the problem comes from the antenna feeder, plug-in and high-frequency tuner high-level, high-AGC and other high-frequency system. (2) If the picture has no “snowflakes” (or sparse) and the contrast is weak and the image is light, the problem is caused by the mixer stage in the high-frequency tuner, the image rejection and the automatic gain control (AGC) circuit. For the situation (l), you should first check the antenna feeder, plug socket is connected