Boot check, the machine USES SP2A702A, AN662710 integration board, examination revealed TC8839 servo drive chip power feet a decoupling capacitor have leakage, replacement and alcohol washed circuit board electricity after commissioning, fault is still. + 5 v, + 8 basic normal v power supply, + 8 v power voltage before also has a + 15 v. Audio and video output terminals connected good TV VCD machine, the boot, heard a hum TV speakers. Check the audio output circuit, found the VCD audio op-amp KA4558P power and servo + 8 v power sharing. Again when reading the disc + 5 v, + 8 v mains voltage, found + 8 v supply voltage fluctuations as the spindle motor rotation, suspected adverse, three-terminal voltage regulator chip LM7808 + 8 v or fluctuations after replacement. Look up at the front of the rectifier filter circuit, only 1000 u F + 8 v filter capacitor, with a 2200 mu F / 25 v capacitance change after troubleshooting. gaqservice manual download site
Analyzing the machine + 8 v power supply voltage is higher, the manufacturer in order to save costs, using only 1000 mu F capacitor as a filter, when the capacitor capacity fell slightly, namely destabilize + 8 v. Boot into the disc, the power load is light, measure the voltage is normal. Reading, after the power supply load increase cause + 8 v voltage fluctuation, lead to focus servo is not normal, bald jump, djing, couldn't read the disc. Due to the CPU has to judge disc, so don't show no disc.gaqservice manual download site