SONY STR-K840P Protection Mode

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  • Guram
    New Member
    • Jul 2017
    • 4
    • Tbilisi
    #1

    SONY STR-K840P Protection Mode

    SONY Amplifier displays PROTECTED error.
    While checking noble resistors(5W 2-0.22Ohm) I have found one that shows different voltage value on his middle leg(52 V)-others show 3 V.
    I've checked output transistors. They are OK.
    Even though I've replaced resistor it still shows 52 V and amplifier is still in PROTECT mode.
    Any ideas?
    Tags: None
    • momaka
      master hoarder
      • May 2008
      • 12175
      • Bulgaria
      #2
      Re: SONY STR-K840P Protection Mode

      Check the drivers for the output transistors. If blown, they will end up driving the output transistors improperly and causing the DC voltage offset protection to kick in.

        Comment

        • R_J
          Badcaps Legend
          • Jun 2012
          • 9535
          • Canada
          #3
          Re: SONY STR-K840P Protection Mode

          Those are 2 resistors in one package, if you are still getting 50 volts at the center of the two resistors, and the outputs are not open or shorted, check the base voltages.
          The drive ic's could be bad, also then check the 100 ohm resistors on the output transistor base's,

          I would check the solder connections on ic701, 702 & 501, I have seen them go bad. sometimes the actual ic is bad from having the bad connections over time.

            Comment

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