Part-2
In this set, sound processing section is inside the video IF unt [IF201 - IFB 389HS]. Check the voltage at teminal (8) of this unit, (audio out). This voltage should be about [3.6VDC]. This is the audio signal output pin. Electronic volume control is used here. The intensity of audio signal appear at pin (8) will depend upon the applied voltage at terminal (70 of this unit. Check the voltage at this point. It should vary, as we increse the volume of the set, either by its front panel of remote volume control buttons.
This voltage comes from pin number (2) of main system control IC [IC 002 - PCA 84C640P-016]. Being picture is OK, sound must be there, as video IF signal out from the video output will have audio signal with it. Because, audio signal is being modulated with video IF signals. The main function of audio processing section is to seperate and to pr-amplify these signals to sufficiant level to drive the audio output IC.
The voltage at pin number [2] of the system control IC, stated above should vary according to the level of volume we set with panel controls. So if there is no voltage deveation present at termianl (7) of video IF unit, come to this check point at pin number (2) of main system control IC. If voltage varies here with adjusting the controls, and not appear this difference at terminal (7) of VIF module, check [R093 -2K2, R030-3K3, R091 - 1K, C017 - 10MFD 63V and R011 - 100K, Zener diode D200 - 6.2V Zener diode, R 211 - 10K]. Check the Zener diode D200 for short]. Check the assicated components connected to termianl (7), if any.
If all are Ok, and still there is no votage variation at pin (2) of main system control IC, it is defective, and should be repalced. If there is voltage variation at pin (20 of system control and terminal (7) of VIF module, and still there is no sound output, make sure that the video processing section inside the VIF unit is faulty. There is no repair to this unit. It should be replaced with samy number.
In this set, sound processing section is inside the video IF unt [IF201 - IFB 389HS]. Check the voltage at teminal (8) of this unit, (audio out). This voltage should be about [3.6VDC]. This is the audio signal output pin. Electronic volume control is used here. The intensity of audio signal appear at pin (8) will depend upon the applied voltage at terminal (70 of this unit. Check the voltage at this point. It should vary, as we increse the volume of the set, either by its front panel of remote volume control buttons.
This voltage comes from pin number (2) of main system control IC [IC 002 - PCA 84C640P-016]. Being picture is OK, sound must be there, as video IF signal out from the video output will have audio signal with it. Because, audio signal is being modulated with video IF signals. The main function of audio processing section is to seperate and to pr-amplify these signals to sufficiant level to drive the audio output IC.
The voltage at pin number [2] of the system control IC, stated above should vary according to the level of volume we set with panel controls. So if there is no voltage deveation present at termianl (7) of video IF unit, come to this check point at pin number (2) of main system control IC. If voltage varies here with adjusting the controls, and not appear this difference at terminal (7) of VIF module, check [R093 -2K2, R030-3K3, R091 - 1K, C017 - 10MFD 63V and R011 - 100K, Zener diode D200 - 6.2V Zener diode, R 211 - 10K]. Check the Zener diode D200 for short]. Check the assicated components connected to termianl (7), if any.
If all are Ok, and still there is no votage variation at pin (2) of main system control IC, it is defective, and should be repalced. If there is voltage variation at pin (20 of system control and terminal (7) of VIF module, and still there is no sound output, make sure that the video processing section inside the VIF unit is faulty. There is no repair to this unit. It should be replaced with samy number.
