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why are these transistors getting so hot?!

Discussion in 'General Electronics Discussion' started by casulica, Apr 17, 2013.

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  1. casulica

    casulica

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    Apr 17, 2013
    hello everyone!

    I am trying to figure out if this is normal or one of the components failed.
    Those two parts of the schematics are from a JVC RX-8010 receiver.
    I was wondering if these 6 power transistors suppose to be so damn hot that I can't even touch them or its just normal.I have used a infrared thermometer and on the heat sink it reads somewhere around 75 C degrees when the volume is just 1/2 way up.
    Comparing these power transistor with the output transistors, the output ones are just barely reading 25 C degrees.

    thanks!!!
     

    Attached Files:

  2. Raven Luni

    Raven Luni

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    Oct 15, 2011
    Power transistors can get extremely hot. Thats why you must use heatsinks
     
  3. BobK

    BobK

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    Jan 5, 2010
    It does seem strange though that the voltage regulators would get that much hotter than the output transistors.

    Bob
     
  4. casulica

    casulica

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    Apr 17, 2013
    they are attached to heat sinks, thats why I'm asking more experienced guys like you if its normal or not. If its not normal,can anyone tell me where i should start looking for the culprit...

    Thanks!!!
     
  5. BobK

    BobK

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    Jan 5, 2010
    If the amp is working normally, it is likely normal.

    Bob
     
  6. shrtrnd

    shrtrnd

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    Jan 15, 2010
    I've worked on old instruments that used 2N3055's as heaters, to keep the inside of
    the enclosure warm and moisture-free in the wintertime.
     
  7. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    Is the music loud when the transistors are hot?

    Or is it just the setting of the volume control which does it?
     
  8. casulica

    casulica

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    Apr 17, 2013
    Max volume is 90.

    If volume it's kept around 45,temp is 50 to 55 C.
    If volume is as high as 55 then temp is 75+C.
    (I never listen with volume higher than 50-55)

    P.s.: I always listen with EQ off (less stress on speakers and amp,also better sound quality)
     
  9. alfa88

    alfa88

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    Dec 1, 2010
    What is the impedance of your speakers?
     
  10. casulica

    casulica

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    Apr 17, 2013
    8 OHM
     
  11. alfa88

    alfa88

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    Dec 1, 2010
    That's good, so you're not overdriving the amp. If the receiver has a fan insure it's working. I suppose the operative phrase would be, "If it aint broke don't fix it"
     
  12. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Nov 28, 2011
    Have you got an oscilloscope? If so, see whether the amplifier is starting to oscillate at high volume settings.
    Actually that's unlikely, unless the output transistors are getting hot too.

    The positive and negative voltages that feed into those regulators... where do they come from? Is it just a mains transformer, or is there a separate power supply board? In either case, measure the voltage on those rails. If it's a lot higher than it should be, the regulator transistors will dissipate much more power than they should.

    Also check that the unit is not designed (or set) to operate from 110V mains and being operated from 230V mains.
     
    Last edited: Apr 19, 2013
  13. Y2KEDDIE

    Y2KEDDIE

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    Sep 23, 2012
    The (6)transistors you show appear to be power supply regulators for the associated circuitry. Check the voltages on each zener cathode and compre to the voltage at the emmiter of each transistor, they should be close to same. If they are , the regulators are working, but may be overloaded, at which point you should start checking elsewhere. Possibly your output transistors are leaky,etc, That would put excessive load on the regulators. Typically Japanese manufacturers build circuitry to the limits of compnents to save costs. I'm not familar with your model reciever. If older , the outputs maybe class AB, which sacrifices effiency for linearity (less distortion). My Kenwood car stereo output heatsink runs so hot I can not touch it for any length of time, yet it is working perfectly It's critical to keep air flow across your heat sinks .
     
    Last edited: Apr 19, 2013
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