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    Giant FSP Resistors

    What are these gigantic pink resistors FSP used to use in some of their PSUs?



    This one comes from an AOpen branded FSP250-60GTW.

    The colors are, from top to bottom:Red (Auburn), Green, Brown, Gold.

    See attachment for larger image.
    Attached Files
    "We have offered them (the Arabs) a sensible way for so many years. But no, they wanted to fight. Fine! We gave them technology, the latest, the kind even Vietnam didn't have. They had double superiority in tanks and aircraft, triple in artillery, and in air defense and anti-tank weapons they had absolute supremacy. And what? Once again they were beaten. Once again they scrammed [sic]. Once again they screamed for us to come save them. Sadat woke me up in the middle of the night twice over the phone, 'Save me!' He demanded to send Soviet troops, and immediately! No! We are not going to fight for them."

    -Leonid Brezhnev (On the Yom Kippur War)

    #2
    Re: Giant FSP Resistors

    From their position (secondary side) they are probably minimum load resistors, which provide a small amount of load to the power supply allowing it to start with little or no external load.
    Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
    For service manual, schematic, boardview (board view), datasheet, cad - use our search.

    Comment


      #3
      Re: Giant FSP Resistors

      I have another one where some of the thin ceramic has chipped off exposing metal underneath... Is there something of higher quality I can replace these with?
      "We have offered them (the Arabs) a sensible way for so many years. But no, they wanted to fight. Fine! We gave them technology, the latest, the kind even Vietnam didn't have. They had double superiority in tanks and aircraft, triple in artillery, and in air defense and anti-tank weapons they had absolute supremacy. And what? Once again they were beaten. Once again they scrammed [sic]. Once again they screamed for us to come save them. Sadat woke me up in the middle of the night twice over the phone, 'Save me!' He demanded to send Soviet troops, and immediately! No! We are not going to fight for them."

      -Leonid Brezhnev (On the Yom Kippur War)

      Comment


        #4
        Re: Giant FSP Resistors

        That resistor seems to be a 250 ohm one based on the colors you say, probably 5-10w based on the size.

        As it's already said, it's there to provide a minimum load for the power supply, it helps it stabilize the voltages when very little is attached to it, or when in standby for example, when only the 5VSB is used.

        There are various packages, for example wirewound resistors in ceramic package (acting as a heatsink) :



        or thick film resistors that look like this:


        (but these would be bad for you as the wires are much closer in the fsp power supply)

        You can find them on Digikey easily.

        Comment


          #5
          Re: Giant FSP Resistors

          I'm going to guess that the first color is actually brown, which would make it 150 ohms, a standard 5% value (220, 240 and 270 are standard values, but not 250). Actually, the more I think about it, I wonder if the third band (multiplier) might be black, a 15 ohm resistor (or even red-black-gold-gold, a 2 ohm part). I'm going to guess that it is metal oxide film, 5W; I could be wrong, but I don't think that technology/package goes up to 7W or 10W.

          Love those vertical-mount bathtub types mariushm had in his post! Good PCB real estate efficiency, nice cooling air profile. They can be found in 2W, 3W, 5W, 7W and 10W, wire-wound for lower values, and metal oxide film for higher values. Cheaper ones are wire-wound (or film) on a fiber glass core; better ones have a ceramic core. The other ones are in the TO-220 package and need a heatsink to be able to dissipate their rated power.
          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


            #6
            Re: Giant FSP Resistors

            (or even red-black-gold-gold, a 2 ohm part)
            I think this is the closest. It hink it's supposed to be brown black gold gold the more I look at it. This would make it a 1 Ohm Resistor. Does this make any sense? Maybe it's just big because of a high watt rating?
            "We have offered them (the Arabs) a sensible way for so many years. But no, they wanted to fight. Fine! We gave them technology, the latest, the kind even Vietnam didn't have. They had double superiority in tanks and aircraft, triple in artillery, and in air defense and anti-tank weapons they had absolute supremacy. And what? Once again they were beaten. Once again they scrammed [sic]. Once again they screamed for us to come save them. Sadat woke me up in the middle of the night twice over the phone, 'Save me!' He demanded to send Soviet troops, and immediately! No! We are not going to fight for them."

            -Leonid Brezhnev (On the Yom Kippur War)

            Comment


              #7
              Re: Giant FSP Resistors

              Why not lift one leg and test it?
              Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
              For service manual, schematic, boardview (board view), datasheet, cad - use our search.

              Comment


                #8
                Re: Giant FSP Resistors

                Originally posted by tom66
                Why not lift one leg and test it?
                +1

                I regularly replace those minimum load resistors if they dissipate more than 0.5W of power - it's just a waste of power, hurts the overall efficiency, and cooks nearby caps if there are any. If the resistors had low values, generally I try to use 33 to 50 Ohms for 3.3V rail, 50 to 100 Ohms for 5V rail and 5vsb, and 330 Ohms or more for 12V and -12V rails, all 1W parts minimum (or at least 2x the power they will be disippating).

                If a power supply has such huge load resistors, then the designer must have been too lazy to design a proper control loop. Most reputable power supplies have very small load resistors, and they are usually of high resistance too so they don't waste power.

                Comment


                  #9
                  Re: Giant FSP Resistors

                  I thought of 1 ohm as a possibility, but on a 3.3V O/P that would be throwing away 10W, a big waste of power, putting a lot of heat near lytic caps, and if they are using a 10W part to dissipate 10W, that is beyond !
                  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

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