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笔者在多次组装和维修卡拉OK机时,发现M50198延时时间很短,而且还需采用逻辑开关控制,很不方便。为此改用给它输入一个外部时钟频率的方法,不仅效果令人满意,延时可以连续可调,而且还可扩展延时时间(一般在4～120ms范围可调)。使用时可根据个人情况进行调整。电路改制很简单,将原电路M50198第②、③脚之间接入的3.27MHz晶振去掉,在该芯片第③脚接入一只220kΩ电阻接地,它不仅起平衡作用,而且还可抗干扰。CD4046为一只锁相环IC,利用内部的VCO产生1.1MHz频率可调的方波,所需频率
I repeatedly in the assembly and maintenance of karaoke OK machine, found M50198 delay time is very short, but also need to use logic switch control, it is inconvenient. To this end instead of using it to enter an external clock frequency method, not only satisfactory results, the delay can be continuously adjustable, but also extended delay time (usually 4 ~ 120ms adjustable range). Use can be adjusted according to individual circumstances. Circuit restructuring is very simple, the original circuit M50198 ②, ③ 3.27MHz crystal access between the feet removed, the first pin in the chip access a 220kΩ resistor grounding, which not only play a balancing role, but also anti-interference. CD4046 is a phase-locked loop IC, the use of internal VCO 1.1MHz frequency can be generated by the square wave, the required frequency