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KAM KXR1000 amp - one channel in protect mode

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    KAM KXR1000 amp - one channel in protect mode

    I've volunteered to have a look at this amp, which belongs to my local club.

    I've brought it home and opened it up. After blowing out loads of dust, there doesn't seem to be anything obviously wrong. No bloated caps etc.

    Channel A is in protect mode. Channel B worked fine at the club. No change, with no speakers or anything plugged in.

    Any pointers?
    Last edited by oddbodd; 01-23-2014, 08:08 AM.

    #2
    Re: KAM KXR1000 amp - one channel in protect mode

    Any good clear pictures so we know what we are dealing with?
    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: KAM KXR1000 amp - one channel in protect mode

      Here's some I took yesterday. Not brilliant pics, I'm afraid.
      Attached Files

      Comment


        #4
        Re: KAM KXR1000 amp - one channel in protect mode

        Since channel B is working. Compare voltages at the similar points of each channel. Connect a load (speaker) on each channel before turning on the power. I suggest on transistor Collectors and Vcc IC pins. More than likely the problem may be in the Output Stage (ICs or Transistors Shorting)

        Comment


          #5
          Re: KAM KXR1000 amp - one channel in protect mode

          OK, thanks.

          I've now tested the transistors, and found one at T323, which is suspect.

          The readings are:
          - to base and + to emitter = 1732
          - to base and + to collector = 1
          + to base and - to emitter = 704
          + to base and - to collector = 558

          Going by the readings on the other transistors, the - to base and + to emitter reading should be 1, not 1732.

          Does that sound right?
          Attached Files

          Comment


            #6
            Re: KAM KXR1000 amp - one channel in protect mode

            Personally, I prefer to use an analog VOM to test transistors. I would set the VOM on the Rx1K or Rx1000 scale and do my testing.
            First I would remove the transistor out of the cicuit board. If I am to do a quick check I would set my VOM on the Rx1 scale and do an in-circuit check.
            However, removing the transistor under test completely out of the circuit board is best.

            Comment


              #7
              Re: KAM KXR1000 amp - one channel in protect mode

              It is 2SD2083 NPN transistor. Checking part when still on the board is not reliable, since it has two channel, you can do comparison readings of the same transistor to see what you get. Each channel has that speaker protection relay (blue rectangular box), listen to see if the dead channel click on or not.
              Did you try contacting them to see if they are willing to send you the diagram/service manual?
              http://www.kam.co.uk/index.php?actio...product_id=103
              Last edited by budm; 01-24-2014, 01:28 PM.
              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


                #8
                Re: KAM KXR1000 amp - one channel in protect mode

                Thanks guys.

                I did compare the readings with the others, and this is the only one that's suspect.

                I'll check that relay, to see if it's switching. I'm also inclined to remove that transistor and test it off board anyway.

                Edit: I've also requested a schematic/service manual.
                Last edited by oddbodd; 01-25-2014, 05:12 AM.

                Comment


                  #9
                  Re: KAM KXR1000 amp - one channel in protect mode

                  Originally posted by oddbodd View Post
                  Thanks guys.

                  I did compare the readings with the others, and this is the only one that's suspect.

                  I'll check that relay, to see if it's switching. I'm also inclined to remove that transistor and test it off board anyway.

                  Edit: I've also requested a schematic/service manual.
                  With amplifiers, if one transistor is bad, usually more are bad. You should test all the others on that same channel, even the ones not on the heatsink.

                  Otherwise, looks like a decent amp!
                  Muh-soggy-knee

                  Comment


                    #10
                    Re: KAM KXR1000 amp - one channel in protect mode

                    The speaker protection relay that budm mentioned, is not switching.

                    Comment


                      #11
                      Re: KAM KXR1000 amp - one channel in protect mode

                      OK. So the 2SD NPN output transistor is suspect.
                      Then the complemetary 2SA or 2SB PNP output transistor may also have failed.
                      This pair of output transistors would be configured in PUSH-PULL.
                      They are actually Darlington transistors and would test slightly different from a 'normal' transistor.
                      Test the big white resistors also, they may have increased in value or burnt out too. They might be 0.22 Ohms 3 Watt resistors.
                      Yes remove the suspect components from the circuit to test them accurately.
                      Also, test the smaller Driver transistors in the circuit as advised, as they too might have suffered some stress.
                      Remove them from the circuit board for testing and observe their pin positions for re-installing. See if there are any EBC markings on the board's underside and a position drawing on the upperside, to guide you.
                      Test the power Fuses as they should have burnt open to protect the system.
                      Always replace fuses with the same rating.

                      Comment


                        #12
                        Re: KAM KXR1000 amp - one channel in protect mode

                        It probably sensing high DC offset voltage at the output so it stays in protection mode. The circuit is direct couple so testing component in the board will not be reliable, they need to be remove. Darlington has such high current gain, it will not take much leakage current in the bad transistor to cause problem.
                        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


                          #13
                          Re: KAM KXR1000 amp - one channel in protect mode

                          Thanks for that. Lots to check, now.

                          Fuses appear to be OK.

                          Comment


                            #14
                            Re: KAM KXR1000 amp - one channel in protect mode

                            or in any stage from the input forward.
                            i would fire it up and measure from ground to the base of each output transistor.the bad one or the one driven by a bad stage will stand out.
                            Originally posted by budm View Post
                            It probably sensing high DC offset voltage at the output so it stays in protection mode. The circuit is direct couple so testing component in the board will not be reliable, they need to be remove. Darlington has such high current gain, it will not take much leakage current in the bad transistor to cause problem.

                            Comment


                              #15
                              Re: KAM KXR1000 amp - one channel in protect mode

                              Schematic for info.
                              Attached Files

                              Comment


                                #16
                                Re: KAM KXR1000 amp - one channel in protect mode

                                Has anyone got a service manual for this amp, please?

                                Comment


                                  #17
                                  Re: KAM KXR1000 amp - one channel in protect mode

                                  Hi, Did you get anywhere looking for a service manual for the amp? I have the same one and I too have some problems I need to look at, so a manual would be really useful.

                                  Comment


                                    #18
                                    Re: KAM KXR1000 amp - one channel in protect mode

                                    Unfortunately not.

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