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Commodore 1084s-p1 fault with video.

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    Commodore 1084s-p1 fault with video.

    Hi all, i have a 1084s and that was working fine until yesterday. But yesterday monitor is suddenly stopped and faulty now.

    I want simply upload a video about problem, which parts and areas should i check, can anyone help?

    Thanks.


    https://youtu.be/qiizl8iJRLM

    #2
    Re: Commodore 1084s-p1 fault with video.

    it looks like a philips chassis, so it could be the line output transformer failed.

    Comment


      #3
      Re: Commodore 1084s-p1 fault with video.

      I would first check for a shorted horizontal output transistor or maybe a shorted diode in the power supply secondary. Are you getting any secondary voltages? there is a service manual for this monitor
      Being an old monitor I would I would check the small caps in the primary switching circuit and it could also be a bad cap for one if the secodary voltages. This power supply has a triac for over voltage protection and that "might" be the sound you are hearing
      Last edited by R_J; 08-06-2019, 05:50 PM.

      Comment


        #4
        Re: Commodore 1084s-p1 fault with video.

        Originally posted by stj View Post
        it looks like a philips chassis, so it could be the line output transformer failed.
        Yes, it is Philips one. What's the line output transformer, you mean flyback transformer?

        Comment


          #5
          Re: Commodore 1084s-p1 fault with video.

          Originally posted by R_J View Post
          I would first check for a shorted horizontal output transistor or maybe a shorted diode in the power supply secondary. Are you getting any secondary voltages? there is a service manual for this monitor
          Being an old monitor I would I would check the small caps in the primary switching circuit and it could also be a bad cap for one if the secodary voltages. This power supply has a triac for over voltage protection and that "might" be the sound you are hearing
          Thanks for advices. I dont measure any voltages yet. Only visually controlled around pcb and dont noticed any bad looking caps or transistors. I have service manual, will check soon. Thanks again.

          Comment


            #6
            Re: Commodore 1084s-p1 fault with video.

            yes,
            there is a way to test for this.
            but first:

            remove the flyback transistor and test it.
            while it's out, put a 40w lamp ( a traditional one, not led) across the B+ capacitor
            it should light up.

            Comment


              #7
              Re: Commodore 1084s-p1 fault with video.

              Originally posted by stj View Post
              yes,
              there is a way to test for this.
              but first:

              remove the flyback transistor and test it.
              while it's out, put a 40w lamp ( a traditional one, not led) across the B+ capacitor
              it should light up.
              Okay ill try it thanks

              Comment


                #8
                Re: Commodore 1084s-p1 fault with video.

                @stj, I cant spot these points in the pcb, is there any detailed schematics or guide somewhere?

                Comment


                  #9
                  Re: Commodore 1084s-p1 fault with video.

                  manuals
                  Attached Files

                  Comment


                    #10
                    Re: Commodore 1084s-p1 fault with video.

                    thx again, can u give me part numbers in schematics? for example, which one is flyback transistor, 7512?

                    https://imgur.com/a/KKkkpEw
                    Last edited by kadird; 08-12-2019, 06:03 PM. Reason: adding picture

                    Comment


                      #11
                      Re: Commodore 1084s-p1 fault with video.

                      Yes, 7512 is the horizontal output (flyback) transistor

                      Comment


                        #12
                        Re: Commodore 1084s-p1 fault with video.

                        Originally posted by R_J View Post
                        Yes, 7512 is the horizontal output (flyback) transistor
                        okay, which one is B+ cap then?

                        Comment


                          #13
                          Re: Commodore 1084s-p1 fault with video.

                          2520 10uf - you should see 128v across it.

                          Comment


                            #14
                            Re: Commodore 1084s-p1 fault with video.

                            Hello again. I replaced EHT transformer with new one, picture partly came back but another issue appeared now. Here is the video about new situation:

                            https://youtu.be/GIYkvtMsf28

                            Where should i check now? Caps maybe or?

                            Thanks.

                            Comment


                              #15
                              Re: Commodore 1084s-p1 fault with video.

                              I just configure brightness potentiometer on the EHT and problem solved.

                              Comment


                                #16
                                Re: Commodore 1084s-p1 fault with video.

                                you must adjust focus and brightness on the transformer.
                                brightness is often labeled "screen"

                                you need to do focus first, then brightness, then focus again - because they slightly effect each other.

                                Comment


                                  #17
                                  Re: Commodore 1084s-p1 fault with video.

                                  Originally posted by stj View Post
                                  you must adjust focus and brightness on the transformer.
                                  brightness is often labeled "screen"

                                  you need to do focus first, then brightness, then focus again - because they slightly effect each other.
                                  thanks man, i'll do it again this way.

                                  Comment

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