Measured mains rectifier output f300V} end shorted. After preliminary examination Q806 shorted , R802 open. The failure has occurred repeatedly . And each is R802 ( or R801) and Q806 damage. After replacement can work , but soon the failure to reproduce .mNwservice manual download site

    Analysis by these corrupt elements , this failure should be Q806 conduction caused . Pole triggered by Q806 G loop analysis , Q806 and its peripheral circuits in order to prevent the switching power supply control and settings. It works as follows: When the switching power supply control , switching transformer winding voltage abnormally elevated B2 by D814 rectified , filtered DC hypertension C833 , R825, R824 minutes after the voltage pressure also increased , when it 's over D813 when the reverse breakdown voltage , Q805 turns on, the voltage on through R825 C833 , Q805 e, c pole was added to the control electrode of Q806 , Q806 was short trigger conduction 300v voltage rectifier output fuse blows ( or R801, R802 open damaged ) .mNwservice manual download site

    Q806 cause triggering causes conduction , switching power supply protection circuit itself is faulty or there is a fault . After the investigation related components switching power regulator loop transfer investigation found no abnormalities Q806 peripheral components found D813 reverse leakage .mNwservice manual download site

    D813 is the reverse breakdown voltage of 10.8V Zener diode , the reverse leakage when it is not serious , the voltage drop on the R827 reverse leakage current generated is small, not enough to make turns on Q805 , Q806 nor guide pass, then TV can work . When D813 reverse leakage phenomenon exacerbated when the R827 pressure drop increases when the voltage reaches Q805 Q805 conduction conduction . Q806 trigger conduction failure . Since D8l3 reverse leakage was unstable , and therefore more subtle faults .mNwservice manual download site

    D813 replaced with the same tube voltage value, and each of the damaged components replaced. Troubleshooting.

 2    1 2 Next Last