2r55a

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  • mike9h29
    Senior Member
    • Mar 2011
    • 60

    #1

    2r55a

    Hi,

    Can some one give me equivalent to SCK 2R55A please?

    I Think it is a NTC Thermistor (I found this info from a post on this site!)

    Thanks

    Mario
  • Toasty
    Badcaps Legend
    • Jul 2007
    • 4171

    #2
    Re: 2r55a

    SCK-2R55A
    2.5Ω - Zero power resistance (25°C)
    5A - max steady current
    120mΩ - resistance at max current (25°C)
    -40 to +170 °C - operating temp range
    veritas odium parit

    Comment

    • mike9h29
      Senior Member
      • Mar 2011
      • 60

      #3
      Re: 2r55a

      Originally posted by Toasty
      SCK-2R55A
      2.5Ω - Zero power resistance (25°C)
      5A - max steady current
      120mΩ - resistance at max current (25°C)
      -40 to +170 °C - operating temp range
      Thanks for the info.

      I am trying to source this part, but I cant find it on ebay.

      Is there any other part number that is equivalent to this part please?

      Thanks

      Mario

      Comment

      • Toasty
        Badcaps Legend
        • Jul 2007
        • 4171

        #4
        Re: 2r55a

        Using those specs, try DigiKey or Mouser.

        Inrush limiter

        I found 1 that is close.

        Hint: be a little "loose" with the specs.
        Last edited by Toasty; 05-05-2011, 09:09 AM.
        veritas odium parit

        Comment

        • mike9h29
          Senior Member
          • Mar 2011
          • 60

          #5
          Re: 2r55a

          Originally posted by Toasty
          Using those specs, try DigiKey or Mouser.

          Inrush limiter

          I found 1 that is close.

          Hint: be a little "loose" with the specs.
          Thanks. Will check again.

          Is it normal for these to crack when there`s a surge?

          I was testing a TFT PSU that was blowing the fuse every time.

          I fried 5 fuses before I found out that the bridge rectifier is shorted!

          Then I found this part cracked.

          Mario

          Comment

          • Toasty
            Badcaps Legend
            • Jul 2007
            • 4171

            #6
            Re: 2r55a

            heh

            No, it's normal for these to crack when there is a problem... They are in -series- with the hot side (or should be...) of the mains.

            That's why you should be using this circuit to test before fully applying line power. Saves a box of fuses.



            If the light comes on full and stays that way, then there's something wrong on the mains side.

            If it comes on briefly and goes dark/dim (I use a clear bulb), then the mains side is probably fine and the problem lies deeper in the supply.

            Toast
            veritas odium parit

            Comment

            • mike9h29
              Senior Member
              • Mar 2011
              • 60

              #7
              Re: 2r55a

              Originally posted by Toasty
              heh

              No, it's normal for these to crack when there is a problem... They are in -series- with the hot side (or should be...) of the mains.

              That's why you should be using this circuit to test before fully applying line power. Saves a box of fuses.



              If the light comes on full and stays that way, then there's something wrong on the mains side.

              If it comes on briefly and goes dark/dim (I use a clear bulb), then the mains side is probably fine and the problem lies deeper in the supply.

              Toast
              Wow!

              Many thanks for your help.

              Will use the bulb to test psus in the future.

              Mario

              Comment

              • Toasty
                Badcaps Legend
                • Jul 2007
                • 4171

                #8
                Re: 2r55a

                Just change the bulb wattage or add another in parallel to increase the current allowed. Some bigger (wattage) supplies need more *oomph* to get started.

                Did you find the replacement (it was at DigiKey).
                veritas odium parit

                Comment

                • mike9h29
                  Senior Member
                  • Mar 2011
                  • 60

                  #9
                  Re: 2r55a

                  Originally posted by Toasty
                  Just change the bulb wattage or add another in parallel to increase the current allowed. Some bigger (wattage) supplies need more *oomph* to get started.

                  Did you find the replacement (it was at DigiKey).
                  to tell you the truth I did not had time to search for it at Digikey today. Hopfully I will search for it tonight.

                  I have another small question regarding electronics. maybe you can help me please?

                  What is a starting capacitor or resistor please?

                  Thanks

                  Mario

                  Comment

                  • Toasty
                    Badcaps Legend
                    • Jul 2007
                    • 4171

                    #10
                    Re: 2r55a

                    >>What is a starting capacitor or resistor please?<<

                    In what type of device?
                    veritas odium parit

                    Comment

                    • maybenever
                      Senior Member
                      • Dec 2010
                      • 158
                      • USA

                      #11
                      Re: 2r55a

                      In the old days of fuse boxes, my Dad would screw a bulb in place of a fuse, then take the circuit apart until the light when out.
                      No one but he and I could seem to understand it.

                      Comment

                      • Toasty
                        Badcaps Legend
                        • Jul 2007
                        • 4171

                        #12
                        Re: 2r55a

                        Originally posted by maybenever
                        In the old days of fuse boxes, my Dad would screw a bulb in place of a fuse, then take the circuit apart until the light when out.
                        No one but he and I could seem to understand it.
                        Either you lived in an old house.......


                        .....or you've just severely dated yourself...


                        veritas odium parit

                        Comment

                        • mike9h29
                          Senior Member
                          • Mar 2011
                          • 60

                          #13
                          Re: 2r55a

                          Originally posted by Toasty
                          >>What is a starting capacitor or resistor please?<<

                          In what type of device?
                          In a switch mode psu.

                          Comment

                          • Toasty
                            Badcaps Legend
                            • Jul 2007
                            • 4171

                            #14
                            Re: 2r55a

                            The startup resistor would be what gets the main switcher going until the PWM control circuit can take over. That can only happen if there is sufficient voltage to drive the PWM chip. Its a power resistor that is connected to the base/gate of the main switcher.

                            Startup capacitor in smps keeps the PWM controller running (stores energy) until the power fully comes up.
                            Last edited by Toasty; 05-07-2011, 12:28 AM.
                            veritas odium parit

                            Comment

                            • mike9h29
                              Senior Member
                              • Mar 2011
                              • 60

                              #15
                              Re: 2r55a

                              Originally posted by Toasty
                              The startup resistor would be what gets the main switcher going until the PWM control circuit can take over. That can only happen if there is sufficient voltage to drive the PWM chip. Its a power resistor that is connected to the base/gate of the main switcher.

                              Startup capacitor in smps keeps the PWM controller running (stores energy) until the power fully comes up.
                              Thanks again for your detailed reply!

                              So, I have a monitor (I posted in the monitor section already), that works fine if I switch it on 1 second after I switch the wall socket on. But, If I switch the Main Socket on and leave the monitor off for more than 5 seconds, it will not switch on.

                              Could this be a Startup Capacitor / Resistor issue please?

                              Thanks

                              Mario

                              Comment

                              • Toasty
                                Badcaps Legend
                                • Jul 2007
                                • 4171

                                #16
                                Re: 2r55a

                                Not familiar enough with monitors to venture a guess. You need to continue the discussion that you started over there. From what I read, a bad regulator or something on the logic board makes sense.
                                veritas odium parit

                                Comment

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