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故障现象:一台飞利蒲107P型彩显联机后电源有“吱”的启动声,屏幕仍无显示,电源指示灯不亮。分析检修:判断故障出在电源部分,相关电路图如附图所示。工作原理:上电后+300V整流滤波电压加至开关场效应管7105漏极,另一路通过电阻3104加至主电源PWM控制集成块TEA1504第①脚启动端,并通过内部电路对第⑥脚外围2112电容充电,当充至12V左右电压时集成块内部电路起振工作,第④脚输出驱动电压加至开关管7105栅极,主电源起振后开关变压器5101第(11)、(15)脚的感应电压经整流滤波得到12V维持电压送至第⑥脚,以代替启动电压为FEA1504供电,从而保持开关电源的工作状态。开机时电源有“吱”启动声说明整流滤波启动电路正常。怀疑故障在维持电压电路中,测得集成块第⑥脚在开机时有12V左右电压,几秒后电压消失并无维持电压,查外围电路发现6107
Symptom: A Philips 107P-type color display power supply after the “squeak” start sound, the screen is still no display, the power light does not light. Analysis and maintenance: to determine the fault in the power part of the circuit diagram as shown in the attached figure. Working principle: After the power +300 V rectifier filter voltage added to the FET 7105 drain, the other way through the resistor 3104 added to the main power supply PWM control block TEA1504 the first leg start, and through the internal circuit on the sixth pin peripheral 2112 capacitor charging, when charged to about 12V voltage when the integrated block internal circuit start-up work, the fourth pin output drive voltage added to the switch 7105 gate, the main power switch 5101 after the first (11), (15) feet The induced voltage is rectified and filtered, and the voltage is maintained at 12V to the ⑥ pin, so as to replace the starting voltage to power the FEA1504, thereby maintaining the working status of the switching power supply. Power at boot time, “squeak” start sound that the rectifier filter startup circuit is normal. Suspected of failure in the maintenance of the voltage circuit, the measured block ⑥ pin at boot time about 12V voltage disappeared after a few seconds did not maintain the voltage check the external circuit found 6107