According to the fault phenomena, determine the CPU system and decoding circuit is normal, the fault should be in the laser and the servo circuit. The machine laser for KSS - 213 - b, cleaning and fine-tuning of the objective light power potentiometer are invalid. Try out new KSS - 213 - c substitution after troubleshooting. Or will the original KSS - 213 - b baldheaded APC amplifier circuit to TA2109F4, 5 E, F the feet in the resistance between the R157, R158 Ω originally (100 k) after the replacement for the 120 k Ω commissioning, read disk performance basic returned to normal.fShservice manual download site