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Low Sound Level on a old Quasar YTS2623EK

Discussion in 'Electronic Repair' started by Jacques St-Pierre, Dec 13, 2007.

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  1. Hello,

    TV Model:
    Quasar YTS2623EK

    Low Sound Level (half of normal)

    TV enter the shop with a blow out resistor and diode related to the supply
    of the Audio Amp.
    We replace the parts and it was working, but the customer complain the sound
    is too low now.

    We check all parts related to audio, even replace the IC, same result.

    We finally found that the volume is DC controlled via a AN15150114A. If we
    push the DC manually the sound level is quite loud, but the controller chips
    do not goes more than half level.

    Sound raise from 0 to 30 on the on screen display, and stay equal from 30 to
    60. We observe that the DC raise from 0 to 3 volts on the DC control pin of
    the amplifier, while the on screen display raise from 0 to 30, but the DC
    stay stable to 3Vdc from 30 to 60.

    So do anyone know why the AN15150114A is unable to push higher than 3 Vdc?
    Its a sort of PWM control going out of the chips, we can not find any speck
    for that chips. We have no way to find one to check if the chip is OK. This
    is an old unit.

    Everything else is OK.


    Jacques St-Pierre
    Président Directeur Général / Chief Executive Officer
    Tél. : (418) 724-5835
  2. David Farber

    David Farber Guest

    I would check the DC level output with a scope. Is it choppy or filtered?
    Also, check if there is some capacitor in the circuit that has failed. The
    capacitor could be breaking down and limiting the voltage to the audio
    amplifier. Another good test would be to float the pin in question and see
    if the voltage increases without a load on it.

    Good luck.
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