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故障现象:开机后机器无任何反应,冷却风扇不转动。分析检修:从故障现象看,是本机电源出了问题。检查保险丝正常,说明输入回路无严重短路现象,测整流滤波后直流电压300V,两个串联大电解电容两端电压均为150V,说明该部分电路无问题。加电测电源输出电压±12V±5V 均为零。根据维修经验,检查重点应放在电源控制电路和主变换电路。断电检查主变换控制电路逆变功率开关管Q1、Q2,发现均已击穿损坏。因无电路原理图,给检修带来不便,只好根据板上色环电阻的颜色先确定其阻值,然后检查其阻值是否正确,检查中发现 Q2b极至脉冲变压器次级所接的电阻R4已
Symptom: After the machine without any reaction, the cooling fan does not rotate. Analysis and maintenance: From the fault phenomenon, there is a problem with the local power supply. Check the fuse is normal, indicating no serious short circuit input circuit, the measured rectified DC voltage filter 300V, two series electrolytic capacitor voltage across the 150V, indicating that the part of the circuit without problems. Plus power supply test output voltage ± 12V ± 5V are zero. According to the maintenance experience, check the focus should be placed on the power control circuit and the main conversion circuit. Power failure check the main conversion control circuit inverter power switch Q1, Q2, have been found breakdown breakdown. Because there is no circuit diagram, to repair inconvenience, had to color board according to the color of the ring to determine its resistance first, and then check the resistance is correct, found Q2b extremely pulse transformer secondary resistance R4 Already