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    #1

    Looking for basic guide to PSU troubleshooting

    I am wondering if someone can point me to a link that has basic troubleshooting of the PSU and what to look for. ie test for continuity on all transistor legs, if its got continuity its good/no good, put the multimeter in the AC Volts mode, test the stby leg and get xx volts ac.....etc

    Does this make sense...a basic guide to troubleshooting. I thought I saw one here somewhere but for the life of me i cant find it.

    This is such a great forum I have learned so much and saved many monitors from the landfills!
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    #2
    Re: Looking for basic guide to PSU troubleshooting

    Originally posted by DTLMG View Post
    I am wondering if someone can point me to a link that has basic troubleshooting of the PSU and what to look for. ie test for continuity on all transistor legs, if its got continuity its good/no good, put the multimeter in the AC Volts mode, test the stby leg and get xx volts ac.....etc

    Does this make sense...a basic guide to troubleshooting. I thought I saw one here somewhere but for the life of me i cant find it.

    This is such a great forum I have learned so much and saved many monitors from the landfills!
    There are a couple of different approaches to troubleshooting a SMPS. About two years ago I wrote up a walk-through of a power supply. When I posted it I learned the guy had found a blown fuse. No, I don't remember which thread.

    PlainBill
    For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

    Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

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      #3
      Re: Looking for basic guide to PSU troubleshooting

      Originally posted by PlainBill View Post
      No, I don't remember which thread.
      A couple of PlainBill SMPS walkthroughs that I bookmarked (the first one I printed with the schematic to fit one page so I could re-read over and over) ...

      https://www.badcaps.net/forum/showpo...6&postcount=30

      https://www.badcaps.net/forum/showpo...97&postcount=2
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        #4
        Re: Looking for basic guide to PSU troubleshooting

        Thanks, retiredcaps for the links. Both of those give an explanation of what is going on.

        I break power supplies down into two catagories - single stage, and multi-stage. The power supply in a 15 - 23" monitor is most likely single stage. My usual process for troubleshooting those in a case of a 'dead' monitor is
        1. Check for output voltages. If present, check signal card.
        2. Check voltage across the large cap. If it is correct (1.4 times line voltage) Suspect the SMPS controller (step 3). If it is not present, check the fuse.
        3. Look up the datasheet and check Vcc to the SMPS controller.

        Multi-stage monitors are typically in larger TVs and monitors. The standby supply is checked like a single-stage supply. The main supply is often more complex, but always verify the 'On' signal is present. then check the SMPS controller.

        PlainBill
        Last edited by PlainBill; 12-11-2011, 06:09 PM.
        For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

        Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

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          #5
          Re: Looking for basic guide to PSU troubleshooting

          Plain Bill:

          I am a newbie to a lot of this technology. I dont know the difference between a SMPS controller , large cap, or a datasheet for the VCC. So I am going to ask for a huge favor and ask that you folks walk me through a power supply test.

          I assume when you talk about the large cap...you mean that big capacitor on the board that says 450volts... the one that scares the hell outta me. I know my way around a Digital Multimeter as I have had a fluke for years for the repairs on lawn and garden equipment (retired master service technician in the OPE industry/fancy words for small engine mechanic) So am I to assume with the power plugged in and my Digitial Multimeter on AC Volts I should touch my probes to each of the legs of the capacitor to check voltage? In my world unless I was working on generators everything was always DC voltage.

          So if its all right with you guys I am going to take some high quality pics of a power supply that I have here and am going to ask you to walk me through the testing process. I will get pics posted tomorrow.

          Comment

            #6
            Re: Looking for basic guide to PSU troubleshooting

            Originally posted by DTLMG View Post
            I assume when you talk about the large cap...you mean that big capacitor on the board that says 450volts.
            Yes. If there is a PFC, that could go to 330 V DC if you are in North America (120 V AC mains). If there is no PFC, that cap should measure 165 V DC.

            So am I to assume with the power plugged in and my Digitial Multimeter on AC Volts I should touch my probes to each of the legs of the capacitor to check voltage?
            You are measuring rectified DC V across the legs of the largest capacitor.

            120 V AC (main) x 1.414 = 165 V DC rectified

            So measure DC with your Fluke. Black probe (COM) to negative leg of cap. Red probe to positive leg.

            If you have aligator clips with your Fluke, use those.

            PS. Which model Fluke? 87-5?
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            We respectfully ask that you make some time and effort to read some of the guides available for basic troubleshooting. After you have read through them, then ask clarification questions or report your findings.

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              #7
              Re: Looking for basic guide to PSU troubleshooting

              Originally posted by DTLMG View Post
              a basic guide to troubleshooting.
              These 2 threads also talk about guides/books

              https://www.badcaps.net/forum/showthread.php?t=10987

              https://www.badcaps.net/forum/showthread.php?t=12603
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              We respectfully ask that you make some time and effort to read some of the guides available for basic troubleshooting. After you have read through them, then ask clarification questions or report your findings.

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                #8
                Re: Looking for basic guide to PSU troubleshooting

                Whilst I'm trying to suss the fault with my monitors SMPS I have just found this:

                http://www.repairfaq.org/sam/smpsfaq.htm#smpsspsr

                I'm no expert but it's given me some useful pointers so would be worth you having a look.
                System: HP xw6600 Workstation, 650W PSU | 2x Intel Xeon Quad E5440 @2.83GHz | 8x 1GB FB-DDR2 @ 667MHz | Kingston/Intel X25-M 160GB SSD | 2x 1TB Spinpoint F3, RAID0 | 1x 1TB Spinpoint F3, backup | ATI FireGL V7700 512MB | Sony Optiarc DVD +/-RW | Win 7 Ultimate x64 | 2x Dell UltraSharp U2410f | Dell E248WFP

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                  #9
                  Re: Looking for basic guide to PSU troubleshooting

                  Originally posted by DTLMG View Post
                  Plain Bill:

                  I am a newbie to a lot of this technology. I dont know the difference between a SMPS controller , large cap, or a datasheet for the VCC. So I am going to ask for a huge favor and ask that you folks walk me through a power supply test.

                  I assume when you talk about the large cap...you mean that big capacitor on the board that says 450volts... the one that scares the hell outta me. I know my way around a Digital Multimeter as I have had a fluke for years for the repairs on lawn and garden equipment (retired master service technician in the OPE industry/fancy words for small engine mechanic) So am I to assume with the power plugged in and my Digitial Multimeter on AC Volts I should touch my probes to each of the legs of the capacitor to check voltage? In my world unless I was working on generators everything was always DC voltage.

                  So if its all right with you guys I am going to take some high quality pics of a power supply that I have here and am going to ask you to walk me through the testing process. I will get pics posted tomorrow.
                  That is exactly the approach I would suggest. I will note that it is quite likely that you will encounter several different approaches; hopefully one of them will make sense to you.

                  PlainBill
                  Last edited by PlainBill; 12-12-2011, 06:36 AM.
                  For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

                  Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

                  Comment

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