( 3 ) "three noes" repair process " three no" fault most of the power board failure , this time not powered to detect blind , you should "look " to see the power board rectifier bridge , +310 V filter capacitor , MOS tube , switching power supply Are chips and other large power element surface has black, burnt , burst and other anomalies , which can quickly identify the fault zone , narrowing the scope of fault detection , but also to prevent blindness caused by power failure once again to expand , causing a safety hazard. If not abnormal, it can be powered up , measure +5 V (CON4 connector ( 1 ) foot ) voltage is normal, if not normal voltage or no voltage, then the standby power circuit is abnormal . Then measure can turn +310 V (El both ends ) voltage , standby power supply VCC end chip +7.8 V (E6 both ends ) voltage and determines ZD3, U3, T3, R6, R42, L2 , etc. are faulty , repair processes as shown below.

 

(4) +5 V voltage is not normal repair process +5 V voltage is low or unstable generally sampled feedback circuit , power chip oscillator and drive circuit malfunction . Standby power chip can detect VCC terminal +7.8 V (E6 both ends ) voltage , if the voltage is normal , you can determine the fault in the sampling feedback circuit. If not properly detect power chip itself or the main power chip oscillator and driver circuit . Detection step as shown below.

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