Open hood found the plane sound source input selection of IC PT2314,CPU is programming the microcontroller 89C54. Test input signal with 10 μg F/50V to PT2314 23, 242 feet. Sounds normal and without distortion. Holding this decision PT2314 has been corrupted. PT2314, the "fault" excluded.3LWservice manual download site
Ch amplifier, cannot be selected after the crash the sound source and the volume is out of control3LWservice manual download site
Open examination revealed no fracture and components within the machine the appearance of signs of damage, so the amplifier plate completely apart, to check the audio source select the IC PT2314. After power up, check power supply 9V PT2314 ① foot properly, but 25, 272 feet (namely DATA CLK) voltage is 4.2V and 0.4V respectively, obviously 27 foot 0.4V voltage is normal, check toward the CPu down 27 feet. Found a disconnect jumper next to the copper foil. Connected with the Office, everything is normal. This case was due to clock 27 foot line disconnect, PT2314 no instructions from CPU has failed.3LWservice manual download site