According to the symptom analysis, audio power amplifier with overcurrent. Sound increases, resulting in amplifier section current increases, resulting in flow switch power 16V DC output power oscillator; with the increasing voice and sound line output were partially destroyed part of the appropriate working conditions. Automatic shutdown after red light, by detecting the output voltage of the power supply is normal, apparently the first failure is no longer exists. In order to determine fault location, consult the microprocessor N901 (M50436-560SP), conditions of work and working conditions. 5V power supply, II feet, and aim at analog output voltage range, and Krispy Kreme foot switch the foot ping du normal output. Only analogue handling part of the 12V supply voltages is 0V. 12V is Flyback transformer output voltage after rectification by the black-foot V552 voltage regulator are available, check the PIN voltage is 0V, which determine the line output stage does not work.



N501 Cha Hang, field oscillations (D5435) ⑤ foot was floating upwards with increasing sound, when added to the 0.6V, the TV automatically shuts down the machine. Obviously protecting circuit in TV action. Try replacing Zener diode VD501, failure cannot be ruled out.

VD501 cathode and unsolder N501 ⑤ feet. Test machine, no matter how extensive and sound increase how long boot, TVs are working correctly. Focus inspection N501 (D5435) ⑤ pin voltage cause of the rise. Found in the TV working properly, VD501 anode voltage of 12V, when volume increases, the voltage starts to rise. Arising from this root cause is the power supply voltage of the voltage rise upward as the TV volume increases from 125V. When the voltage rises to 135V, N501 (D5435) ⑤ pin voltage rises to 0.6V, automatic protection shut down TV. The random drawing did not mark the power supply output voltage standard values. 125V is not the normal output voltage of the machine then? check the Peony 47C7M11 as drawings, 111V this voltage value, based on the comparison of two machines this voltage value and VD501 voltage value 11V requirements, by using the principle of resistance in series measured, VD501 anode voltage value should be less than 11V correctly, but when the power supply output voltages up to 125V, VD501 negative voltage by calculating 12.08V. The output voltage of 125V is obviously incorrect. Root causes of failures are the result of increased supply voltage. Tuning RP811, no change in output voltage 125V, readjustment, and still do. Switching power supply circuit fault was not in doubt. Removed RP811 check OK, be welded back in place, trying to again test machine, suddenly a Flash of machine has three, the power the Red led goes out. Then find out, the VD807 penetrated; V803ce Breakdown voltage, transmission node positive and negative resistance increased to 15k;V804 at the same time also penetrated. After them individually for new, trimmer RP811, fault completely ruled out.