Thermistor Selection Help Needed

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  • greenknight
    New Member
    • Mar 2017
    • 5
    • usa
    #1

    Thermistor Selection Help Needed

    I'm rebuilding my Dell computer's power supply that failed the other day. :o(

    I discovered some bulging capacitors, and one of its power thermistors fried itself. It's manufactured by the Chinese company, "Thinking," but I can't locate a distributor for them in the US. Mouser.com stocks Semitec thermistors, so I'm trying to select one of theirs as a suitable substitute. So far, I've identified 2 candidates that come close to the Thinking's specifications:

    Original Part
    Part # SCK-057
    Mfgr Thinking
    Zero Power Resistance 5 ohms
    Max Current 7 A
    Thermal Dissipation 20 mW/C
    Thermal Time Constant 65 sec
    Operating Temp -40 - +200 C

    Substitute 1
    Part # 5D2-15LD
    Mfgr Semitec
    Zero Power Resistance 5 ohms
    Max Current 6 A
    Thermal Dissipation 39 mW/C
    Thermal Time Constant 70 sec
    Operating Temp -50 - +200 C

    Substitute 2
    Part # 5D2-18LD
    Mfgr Semitec
    Zero Power Resistance 5 ohms
    Max Current 8 A
    Thermal Dissipation 53 mW/C
    Thermal Time Constant 90 sec
    Operating Temp -50 - +200 C

    I'm not an expert on thermistors being used in this type of an application. Is either one of these Semitec's suitable as a substitute for the Thinking thermistor? What would you recommend I use?

    Thanks for your help!
    Tags: None
    • PeteS in CA
      Badcaps Legend
      • Aug 2005
      • 3579
      • USA, Unsure of Planet
      #2
      Re: Thermistor Selection Help Needed

      Fuses don't blow for no reason - if chosen correctly - and the same goes for thermistors. Be sure you fixed the cause of the fried thermistors before replacing them and applying power. It's probably something on the primary side rather than the output side.

      That said, if #2 fits, go with that,for the higher current rating. Thermistors usually should not act as fuses.
      PeteS in CA

      Power Supplies should be boring: No loud noises, no bright flashes, and no bad smells.
      ****************************
      To kill personal responsibility, initiative or success, punish it by taxing it. To encourage irresponsibility, improvidence, dependence and failure, reward it by subsidizing it.
      ****************************

        Comment

        • greenknight
          New Member
          • Mar 2017
          • 5
          • usa
          #3
          Re: Thermistor Selection Help Needed

          Thank you Pete. This is the second Dell Precision 670 power supply that has failed the exact same way. Manufacturing default? Another ham radio friend of mine recommended I not bother fixing it and to buy a complete replacement.

          BTW, I used to live in Santa Cruz and am a SJSU alumnus. :o)

            Comment

            • PeteS in CA
              Badcaps Legend
              • Aug 2005
              • 3579
              • USA, Unsure of Planet
              #4
              Re: Thermistor Selection Help Needed

              Speaking generally, a lot depends on the availability & cost of a new replacement, the cost to repair, and how long you intend to use the computer. If the PSU is a Delta or a Lite On, speaking generally, they make good stuff. If you have a lot of power drop-outs and surges, I'd suggest considering a UPS.
              PeteS in CA

              Power Supplies should be boring: No loud noises, no bright flashes, and no bad smells.
              ****************************
              To kill personal responsibility, initiative or success, punish it by taxing it. To encourage irresponsibility, improvidence, dependence and failure, reward it by subsidizing it.
              ****************************

                Comment

                • greenknight
                  New Member
                  • Mar 2017
                  • 5
                  • usa
                  #5
                  Re: Thermistor Selection Help Needed

                  A couple of years ago one could buy one of these (Dell N650P-00) for under $100. Now I can't find one under $200, and that's for a refurbished one. :o( Any suggestions?

                    Comment

                    • Per Hansson
                      Super Moderator
                      • Jul 2005
                      • 5895
                      • Sweden
                      #6
                      Re: Thermistor Selection Help Needed

                      Maybe the PSU used for the Precision 470 can be used?
                      Part numbers in this thread, seem much less expensive.

                      https://www.badcaps.net/forum/showthread.php?t=5974
                      "The one who says it cannot be done should never interrupt the one who is doing it."

                        Comment

                        • greenknight
                          New Member
                          • Mar 2017
                          • 5
                          • usa
                          #7
                          Re: Thermistor Selection Help Needed

                          That's a great idea. I'll check it out.
                          Thanks!

                            Comment

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