Car amplifier

Discussion in 'General Electronics Chat' started by imraneesa, Jan 26, 2016.

  1. imraneesa

    Thread Starter Member

    Dec 18, 2014
    185
    4
    Dear Sir,

    I have this car amplifier 'US amps' which is going into protect mode. It is using tl494 pwm IC.

    The pin 16 was going high 12v. so i removed the connection going to the pin and the amp started good. when i removed the connection and checked the voltage on pin 16 and it was still showing 0.8v some times 1v and some times 0.6v. it suppose to be 0v without any input. why is it showing some voltage. what about be wrong? somebody please show some light on this. thank you in advance.


    Regards,
    Imran
     
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,998
    745
  3. imraneesa

    Thread Starter Member

    Dec 18, 2014
    185
    4
    Dear Sir,
    How to find which mosfet is pulling it down. it have total so many mosfets. what about transformer? when i force to ground the pin 16 i am hearing some kind of sound near transformer side. not sure if it is transformer or mosfet. how to find the place where it is pulling down.
     
  4. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,998
    745
    You need to measure the voltages in the circuit first, ideally get a circuit diagram of the car amp.
     
  5. imraneesa

    Thread Starter Member

    Dec 18, 2014
    185
    4
    I dont have circuit diagram. it is not available in the net.
    even though i remove the +input it is still showing 0.6v and also pin 3 is 4.6v which is high also.

    when i remove the connection of pin 16, pin 15 is 2.6v and pin 16 still have 0.6v. dont know where it is pulling. where is the short? all the mosfets looking good.
     
  6. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,998
    745
    You aren't going to be able to repair it without a circuit diagram easily, you're going to have to make voltage tests and post pictures of it, otherwise bin it!
     
  7. tcmtech

    Well-Known Member

    Nov 4, 2013
    2,039
    1,667
    My first suspicion would be that the shorted component is in the audio output side of the amplifier not the power supply side.

    A shorted switching mosfet on the power supply would give you an instant dead short resulting blown fuses or blown up mosfets when you hooked it up to 12 volt power.

    A sort circuit the audio amplifier side would cause the power supply to go into protection mode since a short circuit there is something the power supply has some degree of control over.
     
  8. imraneesa

    Thread Starter Member

    Dec 18, 2014
    185
    4
    i removed all the mosfets and i am still having the same readings. nothing change. so it is not mosfet. and i have checked output transistors but nothing is short. also rectifiers are good too.
     
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