Visual inspection , visible R360, line flyback capacitor (C439, C440, C441) burned severely burned circuit board also . If only simply replace the damaged components , using the same fault will appear shortly . In fact , the root cause of the failure in the switching power supply section. The machine power switching elements arranged crowded portion , the power portion of the resistance used is too small, severe fever , leaving the switching performance parameters of the power element portion . Disconnect the L409 ​​( ie off -line power output section ) , with a 60W bulb false load , power monitors the mains voltage slowly increased from 112V, has been increased to 120 ~ 130V only stable , causing the line flyback capacitor , R418 even line pipe the burned. Switching power supply output voltage is unstable , usually part of a switching power regulator failure , I have replaced all the components parts of the regulator , but the fault remains. Finally, the self-excited oscillation circuit R418 (33Ω/1W) replaced the resistor 150Ω/3W appropriately reduce the self-excited oscillation frequency, the main power supply was stable at 112V.

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