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why are these transistors getting so hot?!

casulica

Apr 17, 2013
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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!!!
 

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Raven Luni

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

BobK

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

Bob
 

casulica

Apr 17, 2013
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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!!!
 

BobK

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

Bob
 

shrtrnd

Jan 15, 2010
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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.
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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Is the music loud when the transistors are hot?

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

casulica

Apr 17, 2013
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Is the music loud when the transistors are hot?

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

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)
 

alfa88

Dec 1, 2010
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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"
 

KrisBlueNZ

Sadly passed away in 2015
Nov 28, 2011
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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.
 
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Y2KEDDIE

Sep 23, 2012
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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 .
 
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