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笔者在一次检修中,偶尔发现图像伴音有突然中断而不久又自动恢复的现象.起初以为是电视台的节目瞬时中断,后来经过检查,发现是键控AGC管(1BG_(18))出现软击穿.这看起来好像是由于晶体管的质量不佳所造成,其实并不一定如此.本文通过对一台仿JD-16型电视机AGC电路的分析,提出用适当增大机中1G_(55)容量和在1BG_(18)基极上串接保护电阻R的方法,来防止该管被击穿或软击穿,从而提高图象的稳定性.(一)基本原理分析线路见图1.这是一个利用行逆程脉冲作开关的闸门式电路.1BG_(10)为闸门(键控)管,1BG_(18)作键控AGC放大,1BG_(11)作延时AGC放大.在无行逆程脉冲和行同步脉冲输入时,1BG_(10)
The author in an overhaul, and occasionally found a sudden interruption of the image sound and soon returned to the phenomenon of spontaneous.It was initially thought that the television program instantaneous interruption, and later checked and found that keyed AGC tube (1BG_ (18)) soft breakdown This seems to be due to poor quality transistors caused, in fact, is not necessarily the case.Based on an imitation of the JD-16 TV AGC circuit analysis, proposed by increasing the machine 1G_ (55) capacity And 1BG_ (18) in series with the base resistor R protection method to prevent the tube breakdown or soft breakdown, thereby enhancing the stability of the image. (A) The basic principle of the circuit shown in Figure 1. This is A gate-type circuit that uses a line-back pulse for switching. 1BG_ (10) is a gate (keyed) tube, 1BG_ (18) is keyed AGC amplification and 1BG_ (11) is delayed by AGC amplification. When pulse and line sync pulse are input, 1BG_ (10)