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Sony Receiver Sound Issues

Discussion in 'Repairing Electronics' started by CalcProgrammer1, Nov 14, 2008.

  1. CalcProgrammer1

    CalcProgrammer1 New Member

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    My parents' Sony surround receiver has a problem. The center channel doesn't play any sound, only making occasional crackling noises when the volume is up. I took it apart, assuming that the output transistors may be bad. Tested all of them with a RadioShack Transistor tester and they all seemed to work. I then switched a pair of them on the board (assuming left and center, swapped them) but wasn't too sure which sets of transistors went to which channel. Either way, after swapping it did the exact same thing (all channels but the center worked fine). Is there any chance that it is the output transistors or is it probably something else (digital signal circuit or something like that)?
     
  2. SYE

    SYE Member

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    Hi,
    Try the obvious first.
    Have you checked the speaker ?
    Try swapping it with one from another channel.
     
  3. CalcProgrammer1

    CalcProgrammer1 New Member

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    Yeah, tried another speaker, tried the center in a different channel. While testing I just took one speaker and switched it between channels and ran the test tone, the speaker works fine on all channels but center.
     
  4. dave

    Dave New Member

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  5. PaulAdman

    PaulAdman New Member

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    Try to change the speaker.
     
  6. CalcProgrammer1

    CalcProgrammer1 New Member

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    You're all missing the point. It is NOT THE SPEAKER! The speaker works FINE on other channels, other speakers work FINE on other channels, and ALL the speakers crackle and don't work on the center channel. By speakers, I'm referring to the 100W Sony speakers it is supposed to work with. They are 8 ohm satellite speakers. I did have a 20W 4 ohm subwoofer speaker from a dead set of PC speakers lying around, and hooked it up to the center. It did "work", but was distorted. There was actually sound coming out of it and you could understand what was being said, so I'm thinking it may not be putting out enough power for the 8 ohm speakers.

    I swapped out every set of transistors and nothing happened, so the output transistors appear to be fine. What else could be limiting the output of an amplifier. I'm also fairly sure it isn't the digital decoder/tuner/output mixer/selector system because at low volumes with a 4 ohm speaker, the center channel seems to work fine (higher ohm speakers and higher volumes either don't work or are distorted while other channels work fine).

    I'm thinking it may be a capacitor, but now I've run out of ideas so I'm just guessing.
     
  7. audioguru

    audioguru Well-Known Member Most Helpful Member

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    I think the output of the defective amplifier has DC on it. Then the 4 ohm speaker reduces the DC voltage enough for the amplifier to play a little but with distortion.
    The amplifier is supposed to have NO DC voltage, maybe only 10mV.
    Something has failed to cause the DC voltage.
     
  8. adudu

    adudu New Member

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