请问电视机黑屏无声音无图像,中间一条白线是什么问题?
推荐回答(1个)
这种电视故障专业术语叫做水平一条亮线,所谓的水平一条亮线故障是指遥控彩电在接收彩色电视信号时,所有频道均能接收到清晰的伴音,屏幕上只有一条水平亮线现象。产生此类现象的故障原因一般均是场扫描组成电路工作异常或某种原因强迫场输出电路停止工作引起场偏转线圈中没有锯齿波电流流过,电子束未作垂直运动所致。
(1)场同步输入电路出现严重漏电或短路、场同步分离电路输出端与地或其他部位短路增色会造成场振荡电路停振,如TA7698AP的场同步信号输入端28脚对地出现短路时,集成块TA7698AP内部振荡电路停振,使其27脚无场频振荡脉冲输出,继而使其24脚无场锯齿波信号输出,场输出电路停止工作而产生水平一条亮线。
(2)场振荡电路(包括场频控制电路)工作异常或其正常工作的供电电压异常引起场振荡不工作均会因无法形成正常的场频脉冲而使场输出电路停止工作。对于不直接设场振荡电路的机型(如采用TA8659/8759机心),其场扫描脉冲是由行频脉冲分频而得,若集成块内部分频电路不良或其正常工作电源(TA8659/8759的61脚)异常,均无法形成正常的场频脉冲从其29脚输出,继而出现水平一条亮线故障现象。
(3)场锯齿波形成电路不良或其正常工作的供电电压异常引起场锯齿波形成电路工作异常均会因无法形成正常的场频锯齿波信号而出现水平一条亮线故障现象。
(4)场激励级电路不良或其正常工作的供电电压异常引起场激励级电路工作异常或不工作,使其因无法输出正常的场激励信号而出现水平一条亮线故障现象。
(5)场输出电路不良或其正常工作的供电电压异常引起无法形成场频锯齿波电流,使场偏转线圈中无驱动电流通过,导致电子束未作垂直运动而出现水平一条亮线故障现象。场输出部分电路在电视机电路中属于大功率电子电路,其故障率较高,故障现象除表现为水平一条亮线外,还可能出现场幅过大或过小、线性不好、图像上方有回扫线或无光栅等故障现象。 目前新型遥控彩电的场输出电路均采用集成块,常见的场输出集成电路主要引脚功能与正常工作电压如附表所示。 (6)场输出部分的末级耦合电容变质开路或偏转线圈电路不良,或维修开关在检修位置漏电等。 (7)视放电路不良或束电流形成电路或自动对比度控制(ACK)电路不良,或亮度异常导致束电流过大时,通过视频/解码集成块内部电路的作用,迫使场频激励信号形成电路停止工作,继而出现水平一条亮线故障现象。如采用三洋A3机心的彩电,当ACK电路出现故障,使LA7680的41脚电压低于3V时,将会引起视频/解码集成块LA7680内部的垂直计算器因电压降低而停止工作,继而出现水平一条亮线,这是A3机心彩电特有的通病;对于主机板采用集成块AN5095/AN5195(如长虹CN-5机心)、AN5192(松下cx-1机心)彩电,当视频放大电路、或束电流形成电路或ACK、ABL电路不良引起此类视频/解码大规模集成块的20脚(维修开关控制端兼任ACK控制输入端)电压低于O.7v时,将自动关闭其58脚的场频激励信号输出,使场输出电路停止工作。 由于视放电路不良等产生一条水平亮线故障现象与场扫描组成电路不良产生的水平亮线存在明显的特征差异,即前者在出现水平亮线之前屏幕上出现很亮的白光栅或过亮的单色光栅,且满屏回扫线,随后很快变暗,最后呈水平一条亮线;而后者则不会出现满幅过亮光栅现象。根据此特征差异可区分故障源是视放电路还是场扫描组成电路。 收起
热心网友| 2013-11-08 13:16 评论 9 2
这个涉及到维修专业,先拍一拍,如能显示,则是虚焊接触不良,如拍不好,则可能是场块坏了,或其他的原因,要专业维修的人员检查才知道。
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