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Help! plz making an amplifier board

Discussion in 'Troubleshooting and Repair' started by akhb76, Jul 11, 2016.

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  1. akhb76


    Jul 11, 2016
    I`m so noob in electronic
    I assembled an Amplifier board and when testing it in low volume everything is fine but when increase volume the sound became corrupted and nothing can be heard from song. when I touch ICs one of them is hot and the other one is cold.
    my power supply is 12v 4Amp and its sure enough also my speaker is strong enough and the problem is surely somewhere in the board.
    I attached some photos from board.
    Note: the missing capacitor is coonected from under board.
    sry for my bad english

    Attached Files:

    Last edited by a moderator: Jul 11, 2016
  2. davenn

    davenn Moderator

    Sep 5, 2009

    you haven't told us quite enough
    what are the IC's show us a schematic of the circuit
    show a photo oc the underside of the board
  3. hevans1944

    hevans1944 Hop - AC8NS

    Jun 21, 2012
    Well, here's a schematic from the vendor's website:


    There should be two of these circuits on the circuit board since this is supposed to be a 50 watt stereo amplifier. My guess (since one of the ICs runs hot) is a shorted electrolytic capacitor, perhaps C9 or C12. Since it's a kit, check to make sure the electrolytic caps are not installed wth the wrong polarity. According to the Google Translate description this is an H-Bridge amplifier, but I don't read Farsi. Here is a better picture of the stereo amplifier, also from the vendor website:

    Last edited: Jul 12, 2016
    akhb76 likes this.
  4. akhb76


    Jul 11, 2016
  5. 73's de Edd

    73's de Edd

    Aug 21, 2015
    You forgot to install capacitor C9 on the board.
    You will get no audio, until you install that electrolytic capacitor .

    Just now read back and caught the bottom install. . .assuming that it's polarity is correct ?

    You have symmetrical use of two amps here.
    Take a meter and place it in it's DC voltage position and test the like voltages between like pins of each I.c.
    Since each voltage would almost be the same, expect very little voltage difference.
    If you experience a significant voltage difference, explore that situation.
    SETS of pins to be tested between would be:
    8-6-7-5-12-1 and 4. the others are being shared connections.

    73's de Edd
    Last edited by a moderator: Jul 16, 2016
  6. davenn

    davenn Moderator

    Sep 5, 2009
    I think you meant C10 ;)

    sorry, you were referring to his original pix

    which of course the speaker is disconnected :)
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