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Faultfinding a Denon AVR-1910 in protection mode

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    Faultfinding a Denon AVR-1910 in protection mode

    Hi all

    First off I've never opened a home theatre amplifier before, and what an appalling sight! Taking this thing apart I can see is going to be an absolute nightmare but I'm hoping to get help in diagnosing the fault nonetheless!

    So I've had my Denon AVR-1910 for about 4 years, hooked up to my PC via toslink cable and connected to two large front speakers, and two surround speakers. No problems up until now when a few nights ago I switched it on and after about 10 seconds started hearing buzzing / interference from the speakers. Then a few seconds later the amp switched itself off and went into a red power led blinking every 0.5 second mode. On looking through the user manual it states either a speaker / speaker cable problem, or the amp has gone into circuit protect mode and must contact Denon.

    I checked all cables and connections and they were fine. So I disconnected everything from the unit completely apart from the power lead and tried turning it on. The main relay clicks as it always does / has done within about 5 seconds, get a solid green power led, but then within another 1-10 seconds the unit will power off and resume the blinking red power led every 0.5 seconds.

    Any subsequent attempts with the speakers plugged back in is the same - buzzing \ static noises from them after 5-10 seconds and then a automatic power off within another 5 seconds.

    So I've watched three Youtube videos of people checking other model Denons, whose insides look completely different to my AVR-1910 to my untrained eye , and a lot seem to end up being a voltage regulator issue.

    I think I've found where these are on this amp but I'm not sure. I know I need to probe with my multimeter and check what voltage is being output on the middle legs for each regulator when the amp is powered on - but I don't know what voltage readout I should be expecting, or what would confirm the problem even. The video I watched showed how to expect about 50-60 volts positive on one regulator, same but negative on the other regulator.

    I've attached pictures of the location of the circuit board I've found these and close ups of the regulators in question. They are 7812A JRC transistors. Allegedly I could get them from here in the UK: https://cpc.farnell.com/stmicroelect...0-3/dp/SC08364

    Although note one of the three is a 7912A.

    So I guess my question is am I on the right track, and can anybody help me with what values would show on the multimeter that prove these transistors are at fault?

    Thanks in advance for any help :-)
    Attached Files
    Last edited by Captain Shonko; 04-14-2021, 01:42 PM.

    #2
    Re: Faultfinding a Denon AVR-1910 in protection mode

    7812 = +12v
    7912 = -12v

    Google those parts for their pinouts so you can measure properly on the device.

    Comment


      #3
      Re: Faultfinding a Denon AVR-1910 in protection mode

      what is the "thing" in the middle picture just above the 3 regulators... it looks like a blown component.

      Comment


        #4
        Re: Faultfinding a Denon AVR-1910 in protection mode

        Originally posted by budwich View Post
        what is the "thing" in the middle picture just above the 3 regulators... it looks like a blown component.
        Sorry budwich, can you point out exactly what "thing" you're referring to?

        Comment


          #5
          Re: Faultfinding a Denon AVR-1910 in protection mode

          Originally posted by mmartell View Post
          7812 = +12v
          7912 = -12v

          Google those parts for their pinouts so you can measure properly on the device.
          So I'm expecting +12v on the 7812, and -12v on the 7912, oh their respective output pins yes?
          Attached Files

          Comment


            #6
            Re: Faultfinding a Denon AVR-1910 in protection mode

            Originally posted by Captain Shonko View Post
            Sorry budwich, can you point out exactly what "thing" you're referring to?
            its just above the three regulators... it looks blown.
            Attached Files

            Comment


              #7
              Re: Faultfinding a Denon AVR-1910 in protection mode

              That's a glass zener diode, looks ok to me.

              Comment


                #8
                Re: Faultfinding a Denon AVR-1910 in protection mode

                probably just the way I looked at the picture and lighting.

                Comment


                  #9
                  Re: Faultfinding a Denon AVR-1910 in protection mode

                  The fault is likely in one of the outputs, One the output board there are small 2 pin plugs, check the voltage on one of the pins as you turn on the amp, this voltage should be close to zero volts, If one is either + or - above a volt, this is likely the output section with the fault.

                  Comment


                    #10
                    Re: Faultfinding a Denon AVR-1910 in protection mode

                    Close up attached of that component above the voltage regs.

                    In fact on looking close up, aren't they burn marks I see on the chassis under the middle chip?

                    Will power her up and check with the probe tomorrow when I have good light, it's no good at night here in this room.

                    Cheers
                    Attached Files

                    Comment


                      #11
                      Re: Faultfinding a Denon AVR-1910 in protection mode

                      There is likely nothing wrong with the regulator ic's . It just looks like a bit of dust on the heat sink compound.

                      Comment


                        #12
                        Re: Faultfinding a Denon AVR-1910 in protection mode

                        Originally posted by Captain Shonko View Post
                        Close up attached of that component above the voltage regs.

                        In fact on looking close up, aren't they burn marks I see on the chassis under the middle chip?

                        Will power her up and check with the probe tomorrow when I have good light, it's no good at night here in this room.

                        Cheers
                        still looks like "broken glass"... if it was a plastic cased component, that would be a sign of failure.

                        Comment


                          #13
                          Re: Faultfinding a Denon AVR-1910 in protection mode

                          I suspect the caps. More suspicious is what looks like custom-branded caps!
                          (not known to be a cap manufacturer)
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                            #14
                            Re: Faultfinding a Denon AVR-1910 in protection mode

                            Ok, I've got the readouts, are the 7912 values looking suspect...?

                            After realising that the pinouts are not the same between a 7812 and 7912 (why would they do that ), I can see that on the INPUT pin on the 7912, it gets negative 20 volts but only for a second or two after powering up the amp. Then my meter just reads "-1", and this is before it has powered down itself.

                            Now I'm only assuming this is wrong based on what happens on the two 7812 input pins. They show a permanent positive 20 volts consistently when the amp is powered on.
                            Attached Files
                            Last edited by Captain Shonko; 04-19-2021, 12:25 PM.

                            Comment


                              #15
                              Re: Faultfinding a Denon AVR-1910 in protection mode

                              Originally posted by R_J View Post
                              The fault is likely in one of the outputs, One the output board there are small 2 pin plugs, check the voltage on one of the pins as you turn on the amp, this voltage should be close to zero volts, If one is either + or - above a volt, this is likely the output section with the fault.
                              Hi R_J

                              I don't even know what / where the "output" board is, note I am a complete noob to this. If it's one of these smaller boards connecting the power cable in and front panel power buttons together then I'm guessing it's the one shown here. Although I see no small 2-pin plugs. Maybe they are there but the line of sight is obscured, I'm getting to the stage to start taking stuff out so will soon know.

                              Cheers
                              Mark
                              Attached Files

                              Comment


                                #16
                                Re: Faultfinding a Denon AVR-1910 in protection mode

                                Look at the first picture in your first post, See that upright board with the large heatsink mounted to it? that is the output board. If you look at that board you will see a small white 2 pin jack (there are no wires attached) this is a test point (don't short the pins together) Just check the voltage on either pin.
                                If you are going to attempt repairs to this amp, you should at least download the service manual.
                                Last edited by R_J; 04-19-2021, 12:55 PM.

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