This machine the left and right channels have no output, manually adjust the volume potentiometer, whatever position transferred, hands let go of its own return to the minimum position. Remote control volume is invalid. Trial found that Zhu suction, relay inside the machine.LHpservice manual download site
LHpservice manual download site
Analysis may be the speaker protection circuit is "failed". May also be main amplifier output zero voltage offset caused by protection. Volume potentiometers are always automatically return to the starting position, you may have won this "fault" led control signal from the microprocessor.LHpservice manual download site
LHpservice manual download site
OCL output voltage power measurement, Shen • 0V,R channel is about -40V and its instability. Judging by the "fault" in the r-channel circuits. To further narrow your "failed" scope to put forward small signal level after most of the connection terminals of the amplifier section disconnect, test-r mono output voltage remains the same, so the "failed" narrowed it down to eyebrow level of the r-channel amplifier section.LHpservice manual download site
LHpservice manual download site
-Amplifier circuit board after the addition installed outside the main channel power amplifier circuit, as well as Golden machine rectifier circuits, surround sound amplifier, the speaker protection circuit. Since no random circuit. According to physical mapping of the r-channel output circuit (see attached map).LHpservice manual download site
LHpservice manual download site
First of all check the Q8 and Q9, QlO beam, Q11, four output tubes. Was no exception. But when the four tubes back to try again after the machine and relays should be able to attract. And after the relay is snap. Volume potentiometer for drive motors also has stopped spinning, this phenomenon indicates that volume potentiometers driven motor relay and turns forever pull-in may not come from the same "failed" reasons, prove correct.LHpservice manual download site
LHpservice manual download site
About measure r still -12V at the output voltage, indicates that relay but absorbs, but "failed" and disappear. Suspected "failure" may be caused by unstable a transistor leakage. Taking into account the power amplifier circuit of the machine is not complicated. Using transistors not much, simply on the channel all transistors remain removed, measured one by one, the results did not find any anomalies.

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