First of all, open lid to check the circuit board components without phenomenon such as charred and blackened, fuses are intact. Dianyuan power supply on test machine, main relay do not snap, check coil resistance is normal, suspect the main relay control circuit has a problem, but check the circuit elements are normal. Then measure the left and right channels, find the midpoint of the upper stage of the l-channel power amplifier circuit voltage for -12V, normal should be 0V. "Failed" l midpoint voltage at the output due to severe disorders lead to main relay not closing. At this point, the "fault" level of the l-channel power amplifier.mN2service manual download site
mN2service manual download site
Spirit of Jane after the first propagation principle, first of all check the power tubes 2SC2921 and 2SAl215. Under weld, Rx1k block measuring the forward and reverse resistance with multimeter correctly, test-tube amplification is also normal, thereby excluding the possibility that power amplifier tube.mN2service manual download site
mN2service manual download site
Then to check its power amplifier. In order to suppress "the drift" to reduce signal distortion, most AV amplifier in its main channel amplifiers, differential amplifier circuit is used for first-grade, dual-tube input complementary symmetry circuit structure of push-pull amplifier with an intermediate stage. First check the differential amplifier circuit and found one. 5551 c, e reverse leakage current between electrodes of transistors. Rx1k gear measurement with multimeter, black table e, when a red table in c pointer deflects leakage resistance around 60k or so.mN2service manual download site
mN2service manual download site
After replacing, try main relay has been able to attract, main-channel playback normally, listen to half an hour, no other side effects.mN2service manual download site
mN2service manual download site
Marvel casual tone control switch on the plate below, but just listen to relay "popping" sound in contact at once flashed an intense arc speaker suddenly changed after an extremely harsh screams "dumb." But after about 2 seconds after appliance to snap again, right channel sound normal, left channel only emits a strong noise, try to turn up the volume to maximum, still only a noise without the normal playback.

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