SMPS shows output voltages within range, yet doesn't boot the system.

Collapse
X
 
  • Time
  • Show
Clear All
new posts
  • helion
    Member
    • Jul 2011
    • 10
    • India

    #1

    SMPS shows output voltages within range, yet doesn't boot the system.

    As the title says, the PSU doesn't boot the system. It only does after CMOS is cleared each time. I tried with a different PSU it worked okay.


    The PSU had apparent leakage from the base of a pair of caps. I replaced them with new ones, yet the same issue persists. It shows voltages on the 12 volts at 11.5 v etc. All of the voltages are alright as per the link below.

    http://pinouts.ru/Power/atxpower_pinout.shtml

    What might be the cause I wonder.

    As to the 'leakage', there are no physical issues with the caps, like bulge or the rubber coming out at the base - only the brown vinyl glue like residue at their base which was not there at the same caps in the PSU which worked to boot normally.

    What tests might I carry out on the PSU to identify the cause?

    The PSU is an ATX 250Watt PSU.
  • Hemingray
    KABOOM!
    • Jul 2010
    • 143
    • USA

    #2
    Re: SMPS shows output voltages within range, yet doesn't boot the system.

    Caps do not have to be bulged/physically leaking to be bad. What brand are they?

    Comment

    • debjit625
      Member
      • Jan 2012
      • 14

      #3
      Re: SMPS shows output voltages within range, yet doesn't boot the system.

      The PSU is an ATX 250Watt PSU.
      250 Watts is not enough for modern PC board,atleast 300 to 450 Watts needed.You can also remove any non necessary peripheral like add on video card to reduce the power consumption for test purpose.

      To test the PSU you can use a load resistor (keep in mind about the wattage).Suppose your PSU says it can source 12Volt at 1Amp use a 12 ohms 12 watt resistor to check,normally 12 ohm resistor will be not available ,so you can use a near range like 15 ohms 10 watts resistor.

      Good Luck
      Last edited by debjit625; 01-12-2012, 08:55 AM.

      Comment

      • PCBONEZ
        Grumpy Old Fart
        • Aug 2005
        • 10661
        • USA

        #4
        Re: SMPS shows output voltages within range, yet doesn't boot the system.

        Originally posted by debjit625
        250 Watts is not enough for modern PC board
        No necessarily true.
        Many modern systems use very little power.
        .
        250 watts is usually enough for modern systems that use an average CPU, 1 HDD, 1 optical, and a modest [or onboard] video card.
        .
        Many come that way from the factory.
        For example most Dell clam-shell systems using C2D come factory with a 210 watt.
        Most of the Atom based systems don't need much either.
        .
        The trick is to have the amps on the correct rails.
        [Meaning use a PSU spec'ed for the system type.]
        An old style 250 watt will be heavy on +5v and be light on +12v.
        Most modern boards need more amps on +12v.
        .
        Now, if you are going to spin a bunch of drives or have some power guzzling CPU or a watt hog video card then 250 watts isn't going to cut it.
        .
        Mann-Made Global Warming.
        - We should be more concerned about the Intellectual Climate.

        -
        Be who you are and say what you feel, because those who mind don't matter and those who matter don't mind.

        - Dr Seuss
        -
        You can teach a man to fish and feed him for life, but if he can't handle sushi you must also teach him to cook.
        -

        Comment

        • PCBONEZ
          Grumpy Old Fart
          • Aug 2005
          • 10661
          • USA

          #5
          Re: SMPS shows output voltages within range, yet doesn't boot the system.

          Originally posted by helion
          As the title says, the PSU doesn't boot the system. It only does after CMOS is cleared each time. I tried with a different PSU it worked okay.


          The PSU had apparent leakage from the base of a pair of caps. I replaced them with new ones, yet the same issue persists. It shows voltages on the 12 volts at 11.5 v etc. All of the voltages are alright as per the link below.

          http://pinouts.ru/Power/atxpower_pinout.shtml

          What might be the cause I wonder.

          As to the 'leakage', there are no physical issues with the caps, like bulge or the rubber coming out at the base - only the brown vinyl glue like residue at their base which was not there at the same caps in the PSU which worked to boot normally.

          What tests might I carry out on the PSU to identify the cause?

          The PSU is an ATX 250Watt PSU.
          The PSU gurus will need more detailed info on the PSU and symptoms before they can help.
          - Photos are good too. [Upload them through 'advanced' screen, don't link.]

          The brown glue is know to become conductive when it gets old.
          .
          Mann-Made Global Warming.
          - We should be more concerned about the Intellectual Climate.

          -
          Be who you are and say what you feel, because those who mind don't matter and those who matter don't mind.

          - Dr Seuss
          -
          You can teach a man to fish and feed him for life, but if he can't handle sushi you must also teach him to cook.
          -

          Comment

          • Th3_uN1Qu3
            Believe in
            • Jul 2010
            • 6031
            • Romania

            #6
            Re: SMPS shows output voltages within range, yet doesn't boot the system.

            Pictures of the power supply guts please. It could be a POWER_OK signal that takes too long to come on or a weak 5vsb rail.
            Originally posted by PeteS in CA
            Remember that by the time consequences of a short-sighted decision are experienced, the idiot who made the bad decision may have already been promoted or moved on to a better job at another company.
            A working TV? How boring!

            Comment

            • helion
              Member
              • Jul 2011
              • 10
              • India

              #7
              Re: SMPS shows output voltages within range, yet doesn't boot the system.

              Pictures from my camera Intel CS630 did not show anything clearly enough, so I dropped the idea of taking pics and posting.

              It is a DEER PCB with DR-200ATX v2.02 printed on it. It was sold as the brand Zebronics here in India. Some browning of the board is there at one of the resistors R66. The caps I removed are of a brand called Viva, and the ones I put in as replacements are Teapo.

              I've used it on a Pentium3 System with only the D815EEA Board, Processor, RAM and the HDD.

              Replacing the PSU is cheap enough but I see that repairing it will be a good exercise too .

              Comment

              • japlytic
                Badcaps Legend
                • Oct 2005
                • 2086
                • Australia

                #8
                Re: SMPS shows output voltages within range, yet doesn't boot the system.

                Deer is a known bad brand of power supply, of which was sold under various brand names.
                My first choice in quality Japanese electrolytics is Nippon Chemi-Con, which has been in business since 1931... the quality of electronics is dependent on the quality of the electrolytics.

                Comment

                • helion
                  Member
                  • Jul 2011
                  • 10
                  • India

                  #9
                  Re: SMPS shows output voltages within range, yet doesn't boot the system.

                  Update:

                  I have been rechecking the voltages on the PSU, and I now find that the 12v rail shows 11.07v to 11.13v. The time I first checked and posted this thread, it showed 11.46v to 11.48v.

                  I seem to have 'found the cause' why the PSU did not boot up - the 12v rail. The 5v standby and POWER_OK show unchanging values, at 5.04v. The 3.3 volt rail shows 3.36v and the 5v rail shows 5.24

                  I am beginning to wonder if this can be corrected properly, so that it performs like the other working PSU which consistently shows 11.98 there abouts.

                  Comment

                  • Th3_uN1Qu3
                    Believe in
                    • Jul 2010
                    • 6031
                    • Romania

                    #10
                    Re: SMPS shows output voltages within range, yet doesn't boot the system.

                    Replace the capacitors on the 12v line. But if it has the "diodes-on-a-bracket" thing for 12v, with two diodes in DO-201 package like FR302s or thereabouts soldered to a bracket that is screwed into the heatsink, forget about it.
                    Originally posted by PeteS in CA
                    Remember that by the time consequences of a short-sighted decision are experienced, the idiot who made the bad decision may have already been promoted or moved on to a better job at another company.
                    A working TV? How boring!

                    Comment

                    • kaboom
                      "Oh, Grouchy!"
                      • Jan 2011
                      • 2507
                      • USA

                      #11
                      Re: SMPS shows output voltages within range, yet doesn't boot the system.

                      Don't forget to add:

                      Missing X/Y caps
                      Common-mode filter chokes
                      NTC thermistor
                      "Properly-rated" fuse
                      All small caps

                      Either keep the original heatsinks and use grossly overrated semis, or make/find better ones. In any case, pull any TO-220s out and use TO-247s.

                      Oh Deer, how else can we improve it? How about some real wires, not that 22awg aluminum- with all the ampacity of 24awg copper.

                      Way to
                      "pokemon go... to hell!"

                      EOL it...
                      Originally posted by shango066
                      All style and no substance.
                      Originally posted by smashstuff30
                      guilty,guilty,guilty,guilty!
                      guilty of being cheap-made!

                      Comment

                      • helion
                        Member
                        • Jul 2011
                        • 10
                        • India

                        #12
                        Re: SMPS shows output voltages within range, yet doesn't boot the system.

                        Originally posted by Th3_uN1Qu3
                        Replace the capacitors on the 12v line. But if it has the "diodes-on-a-bracket" thing for 12v, with two diodes in DO-201 package like FR302s or thereabouts soldered to a bracket that is screwed into the heatsink, forget about it.
                        Well, that is the case.

                        I'm going to now replace the PSU itself following your suggestion of giving up attempts at this one. However, I would want to know why it leaves no other options. Is it the economics, or is it that any further investigation would be too tedious/complicated/uncertain?

                        Comment

                        • Th3_uN1Qu3
                          Believe in
                          • Jul 2010
                          • 6031
                          • Romania

                          #13
                          Re: SMPS shows output voltages within range, yet doesn't boot the system.

                          Purely economic. The circuit is very simple, but it would take a lot of work to make it do something useful. The only situation where it is worth bothering is if you're going to do major mods and use it to power something else than a computer.
                          Originally posted by PeteS in CA
                          Remember that by the time consequences of a short-sighted decision are experienced, the idiot who made the bad decision may have already been promoted or moved on to a better job at another company.
                          A working TV? How boring!

                          Comment

                          Related Topics

                          Collapse

                          • taslan
                            Surface 7 Pro wont boot, shows Logo and immediately turns off
                            by taslan
                            Hello everyone,
                            as stated in the title, my surface 7 pro wont boot anymore.
                            When i press the power button it shows the square windows logo for a second and immediately turtns off again.
                            I dont even have a chance to get into bios or boot from usb.
                            While trying to find help online it was suggested to look for help/repair here on badcaps and it might be a ME Region corruption in bios.
                            I dont know what that is exactly, but i never tinkered with the bios or windows in terms of hacking/patching etc.
                            Bought it directly from microsoft and used it now and then and only...
                            01-16-2025, 01:25 AM
                          • eigma
                            Samsung UN40H5003 boot loop every ~8 seconds
                            by eigma
                            Hi, I rescued a Samsung UN40H5003AF (H = 2014 FHD) from the curb. Symptoms are: standby (red) light comes on, stays on for 8 seconds, flickers off, then comes back on, and the cycle continues.

                            Service manual: https://www.electronica-pt.com/esque...is-u8la-71272/

                            SMPS board: checked voltages, all seem normal (A13V = 12.8V, UD = 3.3V, PWM_BLU = 0.77V, PS_OnOff = 5.5V). Remove 10p cable to main board -> backlight comes on. I think this means SMPS board and backlight are good.

                            Main board: BN94-07592P / BN97-08922R...
                            11-20-2024, 10:31 PM
                          • Francesc V.
                            Computer SMPS has voltages from a moment and then disapear
                            by Francesc V.
                            Hi:

                            I am trying to repair a 1000W cheap power supply, but so far, with no much success.

                            The ATX has stable 5V STBY.
                            When shortening PsuON to ground, it triggers all voltages for a fraction of a second and then disapear (I see the leds flashing for a moment from the ATX tester)


                            - I removed and tested the capacitors. They are OK.
                            - Removed and tested the Output rectifiers from the secondary.
                            - Removed and tested the Mosfets from the primary.
                            - Outputs are not shorted.
                            - Overakk review of the solder joins.

                            ...
                            04-15-2025, 01:54 PM
                          • hinisa
                            Xiaomi router freezes at boot after re-capping
                            by hinisa
                            I'm using Xiaomi Router 4A gigabit edition as wireless repeater. It worked fine for 2 years or so, but last week, wireless started to disappear.

                            When I unplug/replug the power, it was working fine for a day/half a day or so until it freezes again.

                            After testing with different power supply adapters and concluding it wasn't the issue I finally opened the case and this was the situation:



                            Anyway I proceed to clean up the mess and replace all caps but unfortunately it made the situation worse. Now router can't even boot, either it freezes during...
                            07-08-2023, 05:58 AM
                          • Capacitorial
                            Powersupply has all the voltages - Monitor still no power
                            by Capacitorial
                            Hello guys,

                            I have a Philips 240B7QPJEB. The monitor seems completely dead.
                            I opened it and measured the voltages of the powersupply. I found that a mosfet was dead and replaced it.
                            On the connector, that goes to the TCON board, all voltages 15-19V and 5V are present.
                            The small connector on the left of the PSU has two cables with 18V and all the other have 0.2V. It connects on this small connector on the left ontop of the panel. I guess the backlight? Seens fine I guess.
                            The weird thing is, that the Power LED is powered over the TCON board.
                            On The TCON...
                            12-28-2024, 02:12 PM
                          • Loading...
                          • No more items.
                          Working...