Recently i repaired a NEC TV 21 CRT and this is the story that how i have fixed this issue.
The sound of this tv was not stable. Sometime good and other time not. After i opened the tv first i checked the speaker (tv is off) the label of speaker indicated that the speaker must be 8 ohm. My ohmmeter confirmed this, when the sound of tv got problem and speaker is ok the most problematic part could be the sound ic amplifier. Since i did not find any diagram for this i asked which ic is sound ic?

sound ic
By following the speaker wires back ward from pins of speaker to main pcb and following the circuit on the pcb lines i directed to IC TDA 7245… which must be checked?
By searching Google, i found that this is sound amplifier ic. And by diagram and data
from google i found out that the pin 3 of ic is vcc and pin 2 is sound output.  Supply voltage is between 14-30 volt dc. I turn on the tv and by measuring the voltage
of pin 3 my volt meter confirmed that the voltage is good enough. And then my scope confirmed that the ic does not have any output .  By changing the ic with a good one the sound return to normal.

About

Beh is from Iran and he loves electronics repair.

One comment on “NO SOUND IN TV BUT THE PICTURE IS GOOD

  1. reza says:

    hi mr beh rasteen
    this article is very good.

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