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  1. #1
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    TDA7294 problem low sound

    hi
    i build an amplifire with tda7294 and connect input of amp to output of y laptop and connect output of amplifire to a 4ohm/50watt speaker and put the volume of my laptop at max and the speaker sound like a 5watt speaker and after 60 second tda7294 with a huge cpu heatsink beacome very very very hot and output sound was about 5 watt
    the power supply was +-33 volts and there wasnt any addotional circuit and build amplifire with datasheet circuit.input signal was at high level

    so please help me where is the problem????

    •   Alt23rd September 2016, 18:48

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  2. #2
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    Re: TDA7294 problem low sound

    Did you use the recommended pcb design shown in the datasheet? If you made a different pcb design then the amplifier might be oscillating at a high frequency which will cause it to get very hot.



    •   Alt23rd September 2016, 20:23

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  3. #3
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    Re: TDA7294 problem low sound

    Hi,

    Show your exact circuit. All known voltages, signals and connections.
    Maybe an additional picture.

    Klaus



    •   Alt23rd September 2016, 20:23

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  4. #4
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    Re: TDA7294 problem low sound

    Choice of two problems:- 1 there is a wiring fault, 2 bad layout or decoupling causing high frequency oscillations. So if you have a scope put it on the output see if you can see any wave form with no input. If its oscillating then the wave form is normally huge like+- Vcc p-p. in this case the layout and or decoupling is wrong. Often touching a sensitive part of the circuit will change the frequency or stop it, use a screwdriver. If your wiring is rubbish you might have wired it up wrong and used positive feedback instead of negative. If you have no scope build a high frequency detector, .1Mf, one end as input other side going to a diode to earth, junction of diode going of to your DVM on DCV via a 10K other side of DVM going to earth. Polarity depends on which the diodes connected. To test probe use the input signal, should get a reading.
    Measure the Vcc, disconnect the amp, Vcc should not change by more then a few volts.
    I am dubious about your heat sink, a big one is 250mm X 250mm X 75 mm, CPU heat sinks tend to be a lot smaller (100mm square) but fan cooled.
    Frank



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