Normal image, indicating that the decompression circuit before and the normal work of the circuit, the fault should be in the six channel audio DAC circuit (U6), three pieces of Dual OP AMP U16, u24 and u25 (c4558), audio mute mute control circuit. In AC-3 DVD playback, pilot device for measuring 5.1 channel audio output terminals are no analog audio signal output, then check the output of the three pieces of Dual OP AMP U16, u24 1, 7 feet have an output end, show that fault in the U16, u24 and u25 1, 7 feet of lag of audio signal transmission circuit, may be the signal coupling resistance open circuit caused by interruption of the audio signal, could also produce squelch circuit error control, the audio signal bypass to the ground. And considering the six way signal coupling resistance element and open is not a possibility, six squelch control tube q35, q36, q39 ~ q42 also the possibility of breakdown is not large, so doubt squelch control circuit is a fault.xunservice manual download site
The squelch control circuit shown in Figure 7 (draw only the front left, front right two channel, other channels and the same). Q36, E32 mutant E32 electrolysis; (R92 to squelch,,, the foot of the squelch control circuit consists of a single chip MT1369EE67 Q32~Q34 q35 q36 element composition, with open / closed static noise and system output approximately 12V voltage is divided into two paths, one is added to the Q33 emitter, and the other path is applied to the resistive E32 100&mICro F/16V capacitance of E32 charging, the voltage will not, at this time E32 cathode voltage slowly rise, Q33 base voltage is determined by the cathode voltage through a resistor r94, Q33 base voltage is lower than the emitter, so Q33 saturated conduction, the collector output approximately 12V voltage through the R38 r84, q35 saturated, remove a boot may be caused by the impact of noise. With the charge charge on the E32 capacitor increases gradually, the base voltage of Q33 will gradually rise, when the difference between the 0.5V and the emitter voltage is less than Q33, the becomes the cut-off and relieves the mute.. (2) turn off silent. Normal DVD + 5V through diode D18 charging the E37, E37 charged voltage around 4.7V to q32 base provides the bias voltage (about 4.8V). At this time, the q32 base voltage slightly higher than the emitter voltage; q32 in cut-off state; when turned off, + 5V 0V. E37 charge voltage q32 provides positive bias voltage, the q32 conduction, E37 positive voltage q32 e - C, D19, R83 r84 enable q36 (q35) conduction, eliminate shutdown may cause noise. (3) squelch system. When need to mute control (such as selections, slow play, fast forward, rewind, etc.), MT1369EE67 foot output low level, q34 conduction, so that the q35, q36 conduction, U161 feet and 7 feet in the output of two-way audio signal AC bypass, squelch to achieve the objective.

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