4.确诊多种缺点综合症
下面经过CVT035型晶体管直流驱动器的典型实例,阐明多种缺点综合症的确诊办法。该缺点伺服板,经开始查看看出,电路板外观很脏,输出级烧损严峻,可见用户的维护养护对比短缺,处理这种缺点,应当首要铲除脏物,修正输出级,切忌轻率通电,不然也许致使短路,扩展缺点面。例如铁粉尘埃的导电短路,输出级开关管击穿对前级和电源的短路等等。经上述处理后,通电查看又发现如下缺点:(1)“欠压”红灯有时闪亮(“READY”绿灯闪灭);(2)电机不转;(3)开关电源(±15V)变压器Tl和电源开关管V69反常发烫。
这是一例典型的综合症,而且缺点之间也许存在某种因果关系,所以处理缺点需求顺序进行,不然也许得不偿失,乃至致使缺点面扩展。咱们经过剖析,做出如下修理排序:开关电源一>“欠压”灯——>电机工作。首要查看电源板,经过丈量主回路150V直流电压和断开±15V负载的查看后,得知缺点在开关电源板内部,在查看电源板中发现10V稳压管V32的电压只要9.5V,由此查看下去,找到缺点因素:V32的限流电阻Rl85阻值变大。替换Rl85后,±15V电源板和“欠压”灯等均康复正常,但电机仍不转。可见,以上灯闪和元件发烫均由Rl85变值致使,电机不转则还有因素。按一般的查看办法,能够逐级查看,但因为经历的因素,咱们只做简略的改换转向实验,成果发现反向工作正常,所以很快查出缺点因素:换向电路的集成块N5(TL084)失效,替换N5后,一切正常。
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