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长虹CHD-TM201B3液晶彩电,图像、伴音正常,用遥控器操作各项功能正常,而使用本机面板按键无法控制,完全失灵。分析与检修:首先按键板插座XK01接触良好,检查按键电源供电电压5 V正常,检查按键上拉电阻R84~R90良好,测量U18(PWll3)的⑦~⑩脚电压正常,拔掉XK01按键插头,测量U18的②~⑩脚的正向对地电阻为2.1 kΩ(正常值为ll kΩ,相差较大),故怀疑U18局部损坏。更换U18后,故障排除。
Changhong CHD-TM201B3 LCD TV, images, sound normal, with the remote control to operate the normal function, and the use of the local panel buttons can not control, complete failure. Analysis and Overhaul: First press the key board socket XK01 good contact, check the key power supply voltage 5 V normal, check the button pull-up resistor R84 ~ R90 good, measuring U18 (PWll3) ⑦ ~ ⑩ pin voltage is normal, unplug the XK01 button plug, Measuring U18 ② ~ ⑩ foot forward to ground resistance of 2.1 kΩ (normal value is ll kΩ, a large difference), it is suspected U18 local damage. After replacing U18, troubleshooting.