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Sony STR-KM7 Not Powering On

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    #1

    Sony STR-KM7 Not Powering On

    So I have a Sony STR-KM7 with mains power - confirmed 240v - has no standby.
    The relay RY901 - standby relay for allowing 240v to main transformer is not switching. No clicking sounds at all when mains power is supplied. No display and no illumination of any LED lights - nothing completely dead.
    I have tested mains power circuit at mains connector on power avideo board - which is where the mains power comes into this unit and this tests good.

    Tested Secondary side of T902 Power Transformer (sub) across terminals - 10.5v

    Tested each secondary winding to ground is 5.25v.
    Tested D904 on diode mode with DMM - .566v
    Tested out of circuit - Q902 - B to E .725v - B to C .725v
    Tested out of circuit - Q901 - B to E .725v - B to C .725v
    Tested RY901 DC coil - 5v - with external power supply - working.

    Now I am completely out of my depth as I cant seem to move forward from here as I believe all these tests are ok. Does anyone know of the operating startup proceedure that can help or even where I should check next.

    I have attached a photo of the power avideo board and the schematic I am usng for reference.
    Attached Files
    Tags: None
    #2
    Re: Sony STR-KM7 Not Powering On

    Can you please upload the service manual/schematic?
    Never stop learning
    Basic LCD TV and Monitor troubleshooting guides.
    http://www.badcaps.net/forum/showthr...956#post305956

    Voltage Regulator (LDO) testing:
    http://www.badcaps.net/forum/showthr...999#post300999

    Inverter testing using old CFL:
    http://www.badcaps.net/forum/showthr...er+testing+cfl

    Tear down pictures : Hit the ">" Show Albums and stories" on the left side
    http://s807.photobucket.com/user/budm/library/

    TV Factory reset codes listing:
    http://www.badcaps.net/forum/showthread.php?t=24809

    Comment

      #3
      Re: Sony STR-KM7 Not Powering On

      You should have standby voltage on CN271 pin 5, or across C904, Is it there?

      Comment

        #4
        Re: Sony STR-KM7 Not Powering On

        Here is the full schematic Budm.
        Attached Files

        Comment

          #5
          Re: Sony STR-KM7 Not Powering On

          I will check those R J and get back to you.

          Comment

            #6
            Re: Sony STR-KM7 Not Powering On

            Did you ever solve the problem?
            I have exactly the same issue and would welcome any advice.
            (I know this thread is old).

            Comment

              #7
              Re: Sony STR-KM7 Not Powering On

              Originally posted by R_J View Post
              You should have standby voltage on CN271 pin 5, or across C904, Is it there?
              I have 13.2 v across C904
              and 12.7 v at CL214 (pin 5 on CN271).

              Any ideas?

              Comment

                #8
                Re: Sony STR-KM7 Not Powering On

                Originally posted by Purge98 View Post
                I have 13.2 v across C904
                and 12.7 v at CL214 (pin 5 on CN271).

                Any ideas?
                UPDATE.................................

                I shorted out the relay RY901 output terminals and it works.
                There must be a problem with the signal to the base of transistor Q901 which drives the relay coil. I couldn't be bothered to find out what it was.

                This solution may help mojos911

                Comment

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