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故障现象:开机后图像正常,但满屏幕都是细条纹,看上去很像电源滤波不好,经检查电源滤波电路C_(706)(150μF/400V)电解电容正常,查主电源电压110V、25V也正常,但当查供中放高频头的12V电压时,发现电压偏高,达13V左右,本机此电压由电源输出17.3V电压经滤波后输出12V稳定电压,电压升高后,引起中放自激,当断开TAT680的(20)脚,不加电源,则屏幕1片白,细条纹消失,查V_(701)(2SD313)正常,但查二极管V_(745)(DX0068CE)已环。从电路上看,这是一只特殊二极管,它的正向压降有3.7V,现在市面上不容易买到这种二极管,可利用普通二极管正向压降0.7V的特点,用4只1N400二极管串连后上机,测输出电压11.SV,机器恢复正
Symptom: After boot image is normal, but full screen is thin stripes, looks like the power filter is not good, after checking the power filter circuit C_ (706) (150μF / 400V) electrolytic capacitor normal, check the main power supply voltage 110V, 25V It is normal, but when looking for the release of loft head 12V voltage, found that the voltage is high, up to about 13V, the voltage of this machine from the power output of 17.3V voltage filtered output 12V stable voltage, the voltage rise, causing (701) (2SD313) normal, but check the diode V_ (745) (DX0068CE) has been put off the TAT680 (20) feet, without power supply, the screen a white, thin stripes disappear, ring. From the circuit point of view, this is a special diode, its forward voltage drop of 3.7V, the market is not easy to buy this diode, the use of normal diode forward voltage drop of 0.7V with four 1N400 After the diode series on the machine, measuring output voltage 11.SV, the machine recovered positive