Amplifier output sound distorted

Discussion in 'Technical Repair' started by Electrofoxtechnology, Dec 23, 2018.

  1. Electrofoxtechnology

    Thread Starter New Member

    Dec 23, 2018
    7
    0
    Hello, i m new here ...i come to a stopping point when repairing a power amplifier.... I found and fixed every parts now its not shorted not in protective state....but the problem is ..output sound is distorte.. . Does anyone faced any problem like my?....how to fix this problem?

    [​IMG]

    [​IMG]
    What i noticed was the transistor c5198,a1941 both of them get hot....after powering on....
    [​IMG]
    Can anyone help plz
     
  2. BBee

    Member

    Dec 6, 2018
    35
    7
    You really need to check voltages around the circuit. As the amplifier and components are getting hot you should be able to find the problem. If it is stereo and one channel is Ok you should be able to compare. It may be sensible to limit the current flow to the faulty stage before it blows again. You ideally need a schematic to trace the circuit.

    Tracy
     
  3. Hymie

    Active Member

    Mar 30, 2018
    697
    182
    It is almost impossible to diagnose a faulty circuit based on a photograph of the PCB.

    To investigate the sound distortion, analysis the output signal on a scope would be very helpful.

    But you might be surprised at the assistance you receive from others on this site.

    Knowing whether the distortion is on one of both channels might assist with the fault diagnosis; but if all you have access to is a multimeter – effecting a repair might prove difficult.
     
  4. Electrofoxtechnology

    Thread Starter New Member

    Dec 23, 2018
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    Thanks for the fast reply..i already checked all of the parts. And it on the left side...so i compared with the right side....all parts has been replace with good ones....thats why i asked the question...as i m at a dead end....i have no other idias to fix it....any help?
     
  5. bertus

    Administrator

    Apr 5, 2008
    19,805
    4,111
    Hello,

    Is there a brand and type of the amplifier?
    That way we might find a schematic.

    Bertus
     
  6. Electrofoxtechnology

    Thread Starter New Member

    Dec 23, 2018
    7
    0
    There is no name but you can see the front side its a Chinese made amplifier...see if it helps
     
  7. Electrofoxtechnology

    Thread Starter New Member

    Dec 23, 2018
    7
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    Its a class ab amplifier
     
  8. Hymie

    Active Member

    Mar 30, 2018
    697
    182
    Although very much a guess, given that it is a class a/b amp, I would suspect that for some reason (a faulty driver transistor?) on the faulty channel, only the push or pull output is working (resulting in distortion). A scope would readily identify such a fault.
     
  9. bertus

    Administrator

    Apr 5, 2008
    19,805
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  10. Ylli

    Active Member

    Nov 13, 2015
    725
    213
    Pulled the service manual on the Yamaha XP1000/2500/3500. Quite a complex amplifier. Did you measure the output offsets and idle current?
     
  11. Electrofoxtechnology

    Thread Starter New Member

    Dec 23, 2018
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    0
    can i see the circuit diagram? plz
     
  12. Ylli

    Active Member

    Nov 13, 2015
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  13. Electrofoxtechnology

    Thread Starter New Member

    Dec 23, 2018
    7
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    thats not the same circuit
     
  14. Electrofoxtechnology

    Thread Starter New Member

    Dec 23, 2018
    7
    0
    all 1943 5200 transistor based chincess power amplifier uses kinda same schematics
     
  15. Ylli

    Active Member

    Nov 13, 2015
    725
    213
    There is a "phonic XP2000", but the faceplate looks totally different.
     
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