Konka LCD TV LC32F1000PD automatic shutdown maintenance example - appliance repair - Huaqiang Electronic Network

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After repairing a Konka 32-inch LCD TV, the cold boot picture sounds normal, and it will automatically stop after a while. The indicator light does not illuminate after the stop, no picture is silent. Disassemble and repair, found that the 12V voltage output from the power board after the TV is stopped is normal! Judge the fault on the motherboard. Test the motherboard 35016492 DC-DC chip N805 SY8123 12V to 5V, found that 5V voltage is unstable, has been changing, and sometimes rise to about 7V, then the TV will automatically stop. The 5V rise is generally caused by the upper sampling resistance of FB becoming larger or the lower sampling resistance becoming smaller. Visually check the N805SY8123's 4-pin FB upsampling resistor R817 62K color darkens, suspected damage! Using the air gun to blow down the R817 test, I found that the resistance of R817 varies from 62K to 100K! Use a 47K and 15K resistors in series to replace the R817. Test machine OK.

TV model


5V that keeps changing


Physical map and circuit diagram

Replace the picture after R817

5V output test picture after replacing R817

TV normal work picture