The function of this machine is more and the auxiliary circuit is complex. The two lower boards are filled with a number of small circuit boards, compact structure, the distance between each unit plate, to measure the voltage of each unit circuit board is difficult.

The output voltage of each outlet is normal. CPU board output end socket CN002 pin voltage, found that the 30 foot SCL voltage and 31 foot SDA voltage are low, from normal to 5V about 2.8V. This confirms that the CPU control circuit is faulty. In order to distinguish between CPU itself fault or the controlled circuit fault, the CN002 30, 31 foot and the outer circuit is disconnected, the starting test 30, 31 pin voltage, recovery 5V, indicating that the fault caused by the controlled circuit. The machine is attached to the bus on the bus, and the circuit is on the main board. Welding on the CN002 30, 31 feet, one by one to open to the unit board socket in the bus welding pin, monitoring bus voltage. When the board of the CN1119 A1 to open the CLK and 9 feet DAT feet, 5V bus voltage recovery, the fault in the A1 board. Measure the A1 board on the operating voltage, found that the power of the IC207 no voltage, check the power supply circuit, voltage regulator IC208 (7809) input 1 12V input, the output end of the foot without 9V output. Remove A1 board inspection, the foot solder joint has a ring of fine crack. After welding, the bus voltage is 5V and the fault is eliminated.