Coupling Capacitor In Video Amplifier/Driver Circuit (CRT TV)

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  • Hitto
    Senior Member
    • Apr 2019
    • 95
    • Italy
    #1

    Coupling Capacitor In Video Amplifier/Driver Circuit (CRT TV)

    I'm currently replacing the output capacitors in a LM2437 CRT driver circuit for a TV.

    The datasheet is here:
    https://pdf1.alldatasheet.com/datash...C/LM2437T.html

    From the labels on the PCB of the LM2437 IC the input voltage is 80V.

    Howewer, datasheets and original capacitors on the board suggest 1uF/160V as the output coupling capacitors for RGB signals.

    Here:


    Do you guys think that I can use 1uF/100V capacitors and the datasheet is overrating the voltage? I assume that the maximum voltage on the three lines would be no higher than 80V.
    Last edited by Hitto; 03-04-2020, 05:05 PM.
    Tags: None
    • R_J
      Badcaps Legend
      • Jun 2012
      • 9623
      • Canada
      #2
      Re: Coupling Capacitor In Video Amplifier/Driver Circuit (CRT TV)

      What is the voltage potential between the - and the + of the capacitor?

        Comment

        • Hitto
          Senior Member
          • Apr 2019
          • 95
          • Italy
          #3
          Re: Coupling Capacitor In Video Amplifier/Driver Circuit (CRT TV)

          I cannot measure it unluckily has I would have to solder the shield back again, connect all grounds again and voltages in that area can be quite high.

          Do you think is possible to have higher voltage than supply current?

            Comment

            • R_J
              Badcaps Legend
              • Jun 2012
              • 9623
              • Canada
              #4
              Re: Coupling Capacitor In Video Amplifier/Driver Circuit (CRT TV)

              You need to look at the other end of the capacitor. Just going by your datasheet, I see 120v on the positive side, The monitor voltage could be higher. Why not just use 160v caps?
              Last edited by R_J; 03-04-2020, 06:07 PM.

                Comment

                • Hitto
                  Senior Member
                  • Apr 2019
                  • 95
                  • Italy
                  #5
                  Re: Coupling Capacitor In Video Amplifier/Driver Circuit (CRT TV)

                  My choice of 160V and 250V capacitor is currently limited to capacitors which exhibits mediocre E.S.R. (8 Ohm and 16 Ohm despite them being unused but I'd assume that this is their de facto E.S.R.) and I'm worried that this will cause problems regarding the quality of the video outputs.

                  If you or other members can confirm that video signals do not require low E.S.R. I will use a 160V or 250V part.

                    Comment

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