Observe each switch on the power supply indicator of this machine after the hair orange, red and green light in turn into has been flashing red glow, in a neutral state, and the second boot instantaneous machine with relay, release the action of sound absorption. Aq7service manual download site
 Aq7service manual download site
According to the fault phenomenon, concluded that is likely to be caused by some reason caused a comprehensive standby protection circuit of control. In order to identify what kind of protection circuit control, welding Q857 collector pins, first boot IC1213 6 foot measuring voltage, found the instantaneous jump in boot instantaneous voltage input, the preliminary judgment this machine integrated standby circuit output overvoltage protection circuit boc or main switch power supply + 12 v and + 25 v output voltage or loss of pressure of two kinds of protection circuit has at least one control conditions. Aq7service manual download site
 Aq7service manual download site
In order to identify what kind of protection monitoring circuit control, welding R864, R567 pin, respectively, in turn, disconnect the two protection circuit of the control, it is respectively measured voltage IC1213 6 foot, found that when desoldering R567, voltage constant for Ov IC1213 6 foot, judge line output circuit overvoltage protection function in the boot instantaneous has accused conditions; Although now break operation output overvoltage protection control, but the machine is still in the state of standby protection, so that the comprehensive protection circuit and its protection control branch is still in a state control. Aq7service manual download site
 Aq7service manual download site
Line and caused by circuit analysis shows that the output overvoltage protection circuit is one of the factors of Du + 140 v output voltage is too high, switch power supply is from the machine for at least two kinds of protection circuit control, can be concluded that failure may be the real reason for poor switching power supply voltage regulator control circuit of the output voltage is too high. Therefore, it is + B voltage on both ends of the measuring C833, found on the instant there are more than 150 v dc voltage output, thus judge fault in the main switch power supply voltage control circuit.

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