Boot after degaussing relay continued to issue "tick, tick" sound, the screen has a horizontal bright line flash, remote control and hand control all the failures. According to the phenomenon analysis, the problem may be in the VC bus system and the controlled circuit. Maintenance, open the machine cover, check the field scanning circuit found no fault, then check the power supply part found switch power supply output voltage is also with the sound down jitter, doubt cause noise when switching power supply is closed instantly, check the standby CPU control terminal (18) feet and a degaussing relay control end (24) pin voltage, appear at the same time jitter phenomenon, judgement is correct. CPU power supply voltage 5V normal, the reset end (36) pin voltage is normal. The CPU is a 12C bus control, the normal operating conditions in addition to the power supply voltage, reset voltage and timely clock oscillation must be normal, 12C bus must also be normal. Therefore, the voltage is normal, and the voltage of the SDA (54) pin is SCL (56), and it is found that the voltage is less than 2V and is not stable. Disengaged (56) foot outside circuit measuring pin Voltage 5V, and the outer circuit voltage is still less than 2V, caused by SCL terminal voltage is not normal in the external circuit is described. The CPUVC bus is hung on the bus and then the block is integrated. Usually for judging the I2C bus which integrated block failure lead to voltage is low, the need to individually disconnected the corresponding pins of each integrated block, if the disconnection of an integrated block 12C bus voltage returned to normal, will for the integrated block fault. Investigation, each integrated block corresponding pins are on the isolation resistance is connected, used measure the isolation resistance pressure drop across the way to judge. When the IC304 (22) (220f1) R333 (SCL) is connected to the end of the series is, the pressure drop of about 0.IV (greater than other integrated block isolation resistance of the pressure drop), the fault is judged here. Considering the probability of integrated block damage is small, so the first check the foot to ground and then connect the 5V regulator D015, found that the reverse leakage. After the replacement of the regulator D015, the machine troubleshooting.