According to previous experience, the green light from the control of the power supply, the green light can be lit, it seems that the main control CPU have to open / shut off the command output, controlled power supply should be output. In order to verify the above inference, boot first measured the output of controlled source IC203, IC202 end of + 5V 0V, 12V is negative and results are not normal (see the figure). Analysis principle knowable, only when the main control CPU17 feet is low potential and Q202 conduction, + 5V by D201 and Q202, R203, R216 to Q201, Q203 base, Q201, Q203 conduction, -27V through r209 and r204, Q201 and R218, R218, Q203 were added to IC203 IC202 adjustment end 1 foot, this time controlled power output, that is, the master standby CPU at 17 feet into low potential, the boot should be is a high potential. Based on this principle, the starting voltage on the CPU17 pin is detected, and no high or low level changes are found when the press is pressed. Check CPU 5V power supply and peripheral circuits have no obvious abnormity, use resistance retaining measure 17 foot of ground resistance, has been short, one by one off 17 feet and external circuit connection, then measure still short. But at this point the boot can be normal, just press the button, the screen displays quickly disappeared, but the optical disc is still in high speed rotation, is clearly not controlled by the power. These tests confirm that the CPU power supply control pin to ground has a short circuit, for the local damage. Cut off 17 feet and the connection of the circuit, the machine will be able to work properly. Why pressing the power button, control objects and drawing the circuit diagram of control traffic light conversion, the red light green light conversion circuit is more special, the standby when the foot of the CPU8 low potential (similar to R308 grounding). Q301 guide through, 5V by Q301, were added to the Q302 base, Q302 base very positively skewed conduction, the ground will D307 (green) cathode, the green death. On the contrary, when the CPU8 pin is high, the green light is red and red. The control principle is the same as the power switch control principle. Can you use 8 pin voltage to control the power on the open / off? The experiment proved to be feasible, use a wire 17 feet and 8 foot connected (as shown in the dotted lines) after the test machine, troubleshooting.

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