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Onkyo TX-NR747 Protect Mode

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    Onkyo TX-NR747 Protect Mode

    Hello... I have onkyo tx-nr747 that won't turn on, protection circuit kick in, I check the unit for possible shorted components at the output of the amp, but so far none. But I can measure 22vdc at one of the channel output (SR, please see the attach circuit diagram page 40) in NH terminal 22vdc is present in both ID+ and ID- reference to ground. The rest of the channel those terminals is no voltage. any help is very much appreciated, thank you
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    #2
    Re: Onkyo TX-NR747 Protect Mode

    Is it +22V or - 22V?
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    Basic LCD TV and Monitor troubleshooting guides.
    http://www.badcaps.net/forum/showthr...956#post305956

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      #3
      Re: Onkyo TX-NR747 Protect Mode

      it's +22V in both NH ID+ and ID-

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        #4
        Re: Onkyo TX-NR747 Protect Mode

        update on this problem... the +22vdc at the output of SR channel is gone, and the amplifier not power up. But I'm not satisfied with this fix, Let me share to you the history of this amplifier, the first problem of this amplifier is... it power up and stay at NG:C error code display. meaning Center Channel is no good. I reset the amp. and run the amp diagnostic again aand still NG:C is present. disconnect all the speakers and input cables and run diagnostic again still NG:C error. So I open it and check the center channel i found one resistor with little change in value but upon remving it out the board and checking the service manual and other parameter of the resistor it seems that the resistor is in acceptable value so i put it back and check every single parts in the center channel and found nothing unusual so i put it all together and test it by running diagnostic again... and the error is gone. So I return it to the owner and me myself the one put the wiring back again to make sure everything is done correctly and we test the unit and it works normally. After 4 months the owner call me again and ask my assistance again because the amp will not turn on, so i check it in his house and it's not turning on anymore. Protection circuit kick in again, but this time with no error just shutdown in few seconds. Trying to fix it via control panel, reset, re-diagnose no good because it shut off in a few second, i bring it again to my shop and check the main board for possible shorted part but none... that's the time i try to find some help in this forum. I try my luck in swapping some parts from the good channels to the faulty channel to see if the fault will transfer to the other channel . I start swapping the driver transistors of the good channel to the faulty channel. Before soldering it back i double check both transistors, and they are 100% good. I assemble it, power it up then it power on.
        Last edited by benja1475; 08-12-2020, 03:46 AM.

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          #5
          Re: Onkyo TX-NR747 Protect Mode

          Any explanation for this kind of problem... any input is very much appropriated. This is not a convincing fix.

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