why are these transistors getting so hot?!

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

  1. casulica

    Thread Starter New Member

    Apr 17, 2013
    I am trying to figure out if this is normal or one of the components failed.
    Some people say it's normal some say it's not, I would would really appreciate a second opinion.
    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.

  2. bountyhunter

    Well-Known Member

    Sep 7, 2009
    75C is not an alarming temperature if that's as hot as they get. My guess is they are linear regulators supplying working voltages to circuitry. 75C would be typical.
  3. russ_hensel

    Distinguished Member

    Jan 11, 2009
    Transistors get hot when they dissipate power, over time this is the integeral of V * I
  4. studiot

    AAC Fanatic!

    Nov 9, 2007
    Transistors can safely (to themselves) reach the boiling point of water, however it is unwise to run them at this temperature since their power handling capability degrades with increasing temperature.
    Also for safety reasons we try not to run components in domestic equipment at temperatures that are "too hot to touch".

    So I think that something is amiss in your JVC.

    Two possibilities to investigate.

    Firstly they may be oscillating at high frequency. This draws a lot of power, overheats components and interferes with normal circuit operation.

    Secondly there may be another component somewhere else in the cicuit drawing excessive current, even perhaps one of the bias resistors to these transistors or a leaky capacitor.