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例一故障现象:一台386机开机后无显示,把手放在电源的风扇窗口、无风.卸下电源,接上假负载,用万用表测量电源输出端,表头稍微动一下,无电压输出.故障分析与维修:此电源采用它激式脉冲调宽稳压,控制电路主要由LM339与TL494及相关元件组成.TL494的第八、第十一脚应该输出驱动脉冲,此脉冲分别加到推动管Q3和Q4的基极,Q3和Q4的集电极分别接到推动变压器T2的初级,如图1.因此笔者修理此种电源时,第一步看桥
Case of a failure phenomenon: a 386 machine boot no display, the hand on the power of the fan window, no wind. Remove the power supply, connected to the fake load, with a multimeter to measure the power output, the table a little move, no voltage output Failure Analysis and Maintenance: This power supply uses its exciting pulse width modulation, the control circuit mainly by the LM339 and TL494 and related components. TL494 eighth and eleventh feet should be driven by the output pulse, the pulse were added to promote The base of the tubes Q3 and Q4, the collectors of Q3 and Q4 are respectively connected to the primary of the push transformer T2, as shown in Figure 1. Therefore, when I repair such a power supply, the first step is to look at the bridge