First boot on test D board connectors D7 (1), (2) feet between dc voltage of 0 v, shows that the main switch power supply of rectifier filter circuit does not work, on this basis, combining to press the power switch instantly without relay and action, judge the fault must be some reason cause the power on and off appliances RL801 constant in the reset state. Detection Q852 base voltage of 0 v, and test the microprocessor IC1213 {} 33 feet voltage, found in the second boot moments with instantaneous jump phenomenon, so remote control circuit can output the second boot high level instruction, failure might be a mixture of external IC1213 6 feet to poor protection circuit components caused by misoperation. Try a short wire short ends meet D1104, make constant at 0 V low potential IC1213 6 foot, then boot detection IC1213 {} 33 feet voltage of 4.8 V is normal, then testing relay drive pipe Q852 base voltage of 0.1 V, obviously high level not transmitted to the boot Q852 base. Q856 then measured the base voltage of 0.65 V, explain Q856 is in saturation conduction state, microprocessor output high level of the short circuit. Because the switching power supply and line output circuit did not work, make Q856 base remote power supply is the cause of potential rise over voltage and over voltage protection monitoring element D857 variable values, the leakage or comprehensive protection circuit Q857 beam junction breakdown damage, etc. First measure D857 anode pin voltage of 0.6 V, thus excluding remote power overvoltage, D857 adverse factors, etc. Again Q857 was detected in b, c, e voltage of 4.7 V, 4.5 V, 4.8 V (should be normal, 0 V, 4.8 V to 4.5 V), on the basis of combining the principle of the circuit analysis concluded that Q857 c - e electrode serious leakage, damage to replace the tube after a short boot found after the standby indicator red light-emitting tube instantaneous on the out into a green light is normally on, figure, photoacoustic normally appear at the same time, this time after power down external in IC1213 6 foot jumper, try the reboot, the machine work back to normal.

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