一则故障现象:开机后,传真机发出“吱吱”叫声,且工作失常。分析与检修:打开盖板,测量电源各组输出电压都比正常值低得多。开关变压器初级线圈上并联的C8、R4和Q2组成了阻尼网络,用来减小尖峰幅度及抑制振铃干扰,防止Ql从导通进入截止时在开关变压器的初级绕组产生过高的脉冲电压而击穿开关 A failure phenomenon: boot, fax machine issued “creak ” sounds, and work abnormalities. Analysis and Maintenance: Open the cover, measuring the power output voltage of each group are much lower than normal. Switch transformer primary coil in parallel with the C8, R4 and Q2 form a damping network, used to reduce the peak amplitude and ringing interference suppression, to prevent Ql from the conduction into the cut-off of the primary winding of the switching transformer to produce excessive pulse voltage and Breakthrough switch