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Grundig CUC120 CRT TV

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    Grundig CUC120 CRT TV

    Hi,

    I have CUC120 CRT TV to repair:

    elektrotanya.com/grundig_cuc120.pdf/download.html

    The screen is black ... and we notice from time to time (when
    the image is very brig.) some small part of image.
    Very few dots.

    I tested the G1 2X V , G2 5XX V , Heather, Power Suply ...

    Thank you,

    Ruy

    #2
    Re: Grundig CUC120 CRT TV

    This is a Super Color A 7100

    The other sub-models in pag.1 - pdf
    right bottom

    Comment


      #3
      Re: Grundig CUC120 CRT TV

      Check other voltage rails. Could be bad voltage to the cathode driver transistors.
      "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
      -David VanHorn

      Comment


        #4
        Re: Grundig CUC120 CRT TV

        Originally posted by Agent24 View Post
        Check other voltage rails. Could be bad voltage to the cathode driver transistors.
        Thank you for your comments, info.

        In Pag. 6 ?
        T256X, T257X, T258X - Amplif.

        +C +200V,

        T2597, C259X, R259X, D2599? or


        Contrast - T2533, SSB and SB and all this part ... what is function, purpose?
        In manual I can't see the procedure to setup this Pots.

        Best Regards,
        Ruy

        Comment


          #5
          Re: Grundig CUC120 CRT TV

          NOTE: I would like to edit the msg but it's not possible.

          In Pag. 1, I try test point R, A, D ... with multimeter
          but as you can see in pic 35 and 36, large spikes.
          So the RMS is different from the values.
          What is the Procedure?

          Thank you,

          Ruy

          Comment


            #6
            Re: Grundig CUC120 CRT TV

            Test point D is 200v (15khz) It supplies D2761 (page8) Measure the voltage on C2762. It should be 26 volts DC.
            On page3, check voltage on C332, It should be minus (-) 8volts
            If you have these voltages the flyback/highvoltage circuit is working.
            Last edited by R_J; 08-16-2019, 10:15 AM.

            Comment


              #7
              Re: Grundig CUC120 CRT TV

              I see there is the +C 200v rail to the output transistors but there is also a 12v rail which comes via 820 ohm resistors to the bases of T2566, T2567, T2568. If either rail was bad, you could get this problem where you see only very bright parts of a picture and nothing else.

              Also, have you checked all the voltage rails from Page 3?
              I see there is +C 200V, +A 115v, +M 19v, +B 12v, +G 15v. Are those all OK?

              Also could be the brightness/contrast pot gone open circuit or something I guess, too.
              But check all the voltage rails first.

              Do you have an oscilloscope? That is the best way to check the waveforms shown for the test points.
              "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
              -David VanHorn

              Comment


                #8
                Re: Grundig CUC120 CRT TV

                Originally posted by R_J View Post
                Test point D is 200v (15khz) It supplies D2761 (page8) Measure the voltage on C2762. It should be 26 volts DC.
                On page3, check voltage on C332, It should be minus (-) 8volts
                If you have these voltages the flyback/highvoltage circuit is working.
                Thank you for your comments, info.
                In Sch. is 24V ... ? But in C2762 is 26V?
                OK
                And the rest ... points ...
                In X = 108 V



                Originally posted by Agent24 View Post
                I see there is the +C 200v rail to the output transistors but there is also a 12v rail which comes via 820 ohm resistors to the bases of T2566, T2567, T2568. If either rail was bad, you could get this problem where you see only very bright parts of a picture and nothing else.

                Also, have you checked all the voltage rails from Page 3?
                I see there is +C 200V, +A 115v, +M 19v, +B 12v, +G 15v. Are those all OK?

                Also could be the brightness/contrast pot gone open circuit or something I guess, too.
                But check all the voltage rails first.

                Do you have an oscilloscope? That is the best way to check the waveforms shown for the test points.
                1) T2566, T2567, T2568 -> T2566, T2576, T2586
                Ok I will check.

                2) My Mult. have Max, Min, and Crest.
                The Var. is 1, 2V in +C, +A ... mV in +M, +B, +G

                3) Tested R392, R393, R394, R396.

                4) Yes several, but no Isolation Transformer in this House/Lab

                Best Regards,
                Ruy

                Comment


                  #9
                  Re: Grundig CUC120 CRT TV

                  Thank you for your comments, info.

                  Works




                  Brightness and Colour Pot.: Min -> Max OK

                  Contrast Pot.: Min -> middle ok
                  But I can' rise
                  If I push this Pot. the image:
                  large ...
                  no FOCUS and
                  washed out -> I only see a Blank RASTER.



                  Note: This Model and CUC220, CUC720 almost identical

                  Best Regards,
                  Ruy
                  Last edited by neuron; 09-25-2019, 10:26 AM.

                  Comment


                    #10
                    Re: Grundig CUC120 CRT TV

                    Thank you.


                    Please your comments:

                    Brightness and Colour Pot.: OK
                    But Contrast Pot.: I can' rise no FOCUS and
                    washed out -> I only see a Blank RASTER.

                    Best Regards,
                    Ruy
                    Last edited by neuron; 11-29-2019, 06:20 AM.

                    Comment

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