Audio Amp Problems

Discussion in 'General Electronics Chat' started by krankshaft, Dec 28, 2006.

  1. krankshaft

    Thread Starter New Member

    Dec 28, 2006
    I am working on a Kinyo Gamezone 5.1 : 5 speaker and woofer amplifier TW-527. I recieved it with two dead channels both the high frequency speakers. The line level input signal to the amp is sent to 3 TA8227P dual channel audio amps which drive the speakers.

    Upon replacing one of the ICs I was able to repair one of the channels. However the center channel speaker is giving me a bit of trouble I have replaced that IC as well and still no dice.

    Here is a link to the datasheet for the IC.

    The block diagram for the test circuit in the datasheet is identical to the one I'm working with in the amp.

    On this amp IC since its the center channel only one of the channels is used the other channels input and output is grounded however the capacitors and resistors are there as if they were to receive a signal and output to a speaker however when it comes to the input and output leads themselves as seen in the test circuit they are grounded.

    The following signal measurements I took below with an oscilloscope and my Ipod plugged into the input since I couldn't find my tone generator.

    The upon measuring the + positive input with my scope set to about 10 milliamps per division I'm getting an input signal however when measuring the - negative input I am getting nothing. Upon measuring the output pin I get a bit of deflection not near enough to drive a speaker actually its weaker then the input signal.

    Upon measuring the - negative input on the other working channels I get a signal just like the + positive input signal. The - negative input from the IC goes through a resistor and then is capacitvely coupled to ground. I believe the - negative input sets the gain by taking the signal from the output and feeding it to the input like an opamp.

    However how can it feed anything to the input if I have almost no output :confused:?

    Even stranger when I measure the channel that is not used in the same amp IC I am experiencing something even wierder I have no signal on that channels + positive input however I have some real weak deflection in the 10 millamp range on the - negative input. Upon measuring the output on that channel I am getting a considerable signal amplification in the 20 millamp range.

    This channel of the amp is grounded and not used it shouldn't be getting any signal?

    I feel what ever is causing this is whats causing my problems with the other channel.

    I have read reports of dead channels on these units what could it be?

    Thanks for any help you can offer.
  2. Gadget

    Distinguished Member

    Jan 10, 2006
    For a start, no audio amp (used or not) should have a grounded output. Thats just asking for trouble.
  3. krankshaft

    Thread Starter New Member

    Dec 28, 2006
    Thanks for the tip I have never seen an amps output grounded before and now I know why.

    I am going to try to disconnect the other unused channels input and output pins for the remainder of the tests.

    I have a feeling I'm not combating a defective component here but bad engineering.