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在自制电视机时,往往会遇到行频振铃干扰现象,这种干扰使显象管屏幕上出现异常的黑自带,影响正常收看电视节目。由于行频振铃干扰的产生不但与电路设计、元件选用等有关,也与装配工艺、调试方法有关,因此要排除它并不容易。现在就这个问题作一较为详细的叙述。文中侧重于实际排除干扰的办法。一般行频振铃干扰在电视屏幕上主要有两种表现形式。其一是光栅左方出现几条自左向右逐渐衰减的垂直明暗条(图1),常称为“阻尼振铃条”。这种现象主要是行正程扫描电流阻尼不良所引起的。大家知道,行扫描的锯齿电流分别由行输出管和阻尼管提供各半(图2)。如果阻尼管的阻尼作用不良,将使扫描电流正程前半段有正弦振荡成分(如图2中虚线所示,
In home-made TV sets, often encountered line frequency ringing interference phenomenon, this kind of interference so that the picture tube screen abnormal black self-bringing, affecting normal watching TV programs. Due to the occurrence of line frequency ringing interference not only with the circuit design, component selection, etc., but also with the assembly process, debugging methods, so to exclude it is not easy. Let us now make a more detailed account of this issue. The article focuses on the actual way to eliminate interference. General line frequency ringing interference on the TV screen there are two main manifestations. The first one is the left side of the grating appeared several gradually attenuated from left to right vertical shadows (Figure 1), often referred to as “damping ring bar.” This phenomenon is mainly due to the positive scan current damping caused by poor. As you know, the sawtooth current of the line scan is provided by the row output tube and the damper tube, respectively, in half (Figure 2). If the damping tube damping effect is poor, will make the first half of the scan current positive sinusoidal oscillation component (as shown in Figure 2 dotted line,