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RCA (Thomson) F20TF10 in a coma

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    #141
    Re: RCA (Thomson) F20TF10 in a coma

    Transformer failure probability is very small, 1% of the 100

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      #142
      Re: RCA (Thomson) F20TF10 in a coma

      Yeah, it's more like some failure elsewhere causing the transformer to operate in a more audible mode. Assuming the noise is abnormal from the usual operating noise.
      "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
      -David VanHorn

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        #143
        Re: RCA (Thomson) F20TF10 in a coma

        That's good to know. There may be hope for this thing I am in the process of checking the eletrolytics.

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          #144
          Re: RCA (Thomson) F20TF10 in a coma

          I wonder if something connected to that transformer is shorted?
          "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
          -David VanHorn

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            #145
            Re: RCA (Thomson) F20TF10 in a coma

            I don't know, I couldn't find any pinout or other info on the transformer.

            However, I already found a bad 10uF 250v cap in the horizontal output circuit on the HOT emitter. It was only the 5th cap I pulled to test too. Measures 1uF 250 ohms ESR. I've got an 8uF 450v axial I'm going to substiture there that actually measures 9.5uF. It's much larger but there is room for it if I can wire it in. I also have a couple of 10uF 200v caps but I don't know what the peak voltage is there so don't want to chance it.

            Edit: replacing that cap didn't fix the TV, it's acting exactly the same so back to checking more caps

            The DC voltage across the cap is 134v, do you guys think it'd be ok to use a 200v cap there?

            Edit2: Found another bad cap, I expect to find more.
            Last edited by SteveNielsen; 11-11-2014, 10:02 PM.

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              #146
              Re: RCA (Thomson) F20TF10 in a coma

              8uF 450v it is normal for the replacement a bad 10uF 250v

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                #147
                Re: RCA (Thomson) F20TF10 in a coma

                I have checked everything I am capable of and willing to do on this one. I've checked every electroyltic cap, every discrete non-SMD transistor and diode, many both in and out of circuit, and all the fuses and resistors in the power supply sections, and a lot more other things.

                So I'm giving up, it's no longer worth my effort and I'll move on. I'll salvage some possibly useful parts but it is going to be recycled. It was fun trying, and thanks for the help you guys, especially Kasfamily.

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                  #148
                  Re: RCA (Thomson) F20TF10 in a coma

                  Hi Steve! I also was interested to solve this problem and try to help you. Sometimes even have to repair these old TV. I just wanted to say that for some time I could not participate in the thread. I go on holiday to Egypt in Sharm El Sheikh.

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                    #149
                    Re: RCA (Thomson) F20TF10 in a coma

                    You've been great Kas. I really appreciate the interest and attention and help you've given to me. I have no complaints

                    Have a great holiday in Egypt. Have a great time there!

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