FSP350-60UMDN -12V Question

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  • Solder Boy
    Senior Member
    • Nov 2006
    • 178
    #1

    FSP350-60UMDN -12V Question

    Hi.. I just finished replacing the obvious bad caps in this power supply. Just a little stumped. I have two power supply testers. One that doesn't show voltage readout, the other one that does.

    Anyway on the -12 line the voltage drops to 11.0 volt and goes back to -12 and beeps on the digital readout PSU tester.

    Question is the -12 used on a motherboard? If it was the +12V then I'd be inclined to worry a bit.

    I'm gonna hook it up to a test tower I don't care about and see what happens.

    Just thought I would ask here.

    Thanks
    www.bcrelectronics.ca
    Tags: None
    • Dgtech
      E. Technician
      • Apr 2009
      • 1462
      • Steeler
      #2
      Re: FSP350-60UMDN -12V Question

      Just replacing the "obvious bad caps" is NOT recommended. If I have obvious bad caps, then I will change all of them, or at least check them all with capacitance checker. Sounds like you have a regulation problem. Some caps are for filtering out the fluctuation ( ripple ) in the regulation circuits.
      The strong-minded rise to the challenge of their goals,the weak-minded BECOME HATERS

        Comment

        • Behemot
          Badcaps Legend
          • Dec 2009
          • 4845
          • CZ
          #3
          Re: FSP350-60UMDN -12V Question

          It's usually OK to replace only output caps and these up to whichever capacity.

          You could usually leave the small caps on the regulation circuits Dgtech was talking about since these almost never die. If you want, replace them but with exactly the same capacity.

          On my old Fortrons, the -12 V rail had always some strange readouts when running without load. When I connected the PSU's into motherboards, -12 V was within specs. But I doubt it is being used in last 5 years so be easy with it...
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            Comment

            • 370forlife
              Large Marge
              • Aug 2008
              • 3112
              • United States
              #4
              Re: FSP350-60UMDN -12V Question

              -12v is hardly used and has a + or - 10% tolerance, 11v is fine.

                Comment

                • Solder Boy
                  Senior Member
                  • Nov 2006
                  • 178
                  #5
                  Re: FSP350-60UMDN -12V Question

                  Thanks everyone.. I now see why you said just don't replace the obvious bad caps. Got bored tonight so I decided to practice on "dead" PSU boards for the hell of it.. checked as many of the uber small caps as I could and sure enough just about everyone of them was waaaaaaaay off the ESR scale.. the one baby cap was really bad.. it was in the yellow zone with a reading of 50!

                  I don't have any of these in stock, so over the next little while I will be ordering in the tiny ones.. you know the 0.33 50V ones etc.

                  If I hadn't already of butchered some of these boards they probably could have been fixed.. it was an eye opener for sure!
                  www.bcrelectronics.ca

                    Comment

                    • Agent24
                      I see dead caps
                      • Oct 2007
                      • 4929
                      • New Zealand
                      #6
                      Re: FSP350-60UMDN -12V Question

                      The smaller ones not used in the output are usually general purpose and so aren't meant to have low ESR anyway, but 50 ohm doesn't sound good either.
                      "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
                      -David VanHorn

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