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Help identifying blown component in Dell PSU.

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    #21
    Re: Help identifying blown component in Dell PSU.

    Originally posted by roadrash View Post
    ... what is the ferrite bead for?
    Ferrite beads are often used to slightly slow the turn-on and turn-off of fast switching MOSFETs and rectifiers. Super fast turn-ons and turn-offs tend to cause high frequency ringing, which causes conducted and radiated noise problems.

    As stj seems to be suggesting, that noise can also get into regulator control circuits and cause problems.

    I've also heard of situations where the Miller capacitance and fast voltage rise of fast switching MOSFETs turned the MOSFETs back on as they were being turned off and causing the MOSFETs to short.
    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.
    ****************************

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      #22
      Re: Help identifying blown component in Dell PSU.

      Originally posted by PeteS in CA View Post

      I've also heard of situations where the Miller capacitance and fast voltage rise of fast switching MOSFETs turned the MOSFETs back on as they were being turned off and causing the MOSFETs to short.
      I did read somewhere that Mosfets were a weak point in Dell PSU's at one time and were responsible for many failures. This is probably whats happened to this one by the sound of it. Just need to find out what the identity of this part is. I did find a PSU the same as this cheap in France, so bought it and paid for delivery to the UK. Then the next day I got a email saying my order was canceled and a message from the seller saying I wont send to the UK. well pissed me off..

      Comment


        #23
        Re: Help identifying blown component in Dell PSU.

        Have a look at the TOP227 datasheet and see if the 5VSB circuit in your PSU resembles that of the sample circuit on page 7 of the datasheet. In particular, see if the circuit connecting to the Control pin of the TOP227 IC is similar, as that's the easiest way to tell. Here is the datasheet, by the way:
        https://cdn.badcaps-static.com/pdfs/...e54311a3df.pdf

        I also noted your PSU has some tan/brown conductive glue. Make sure to remove as much of it as you can, especially any on the primary side and any that has turned brown/black. I find the easiest way to do that is to take a small flat head screw driver with a long handle and poke the glue to bits. Then I use tweezers to remove what I can.

        Originally posted by stj
        when the cap dries up they sit and pulse for a while creating a ticking sound - then BANG, your TOPswitch is toast!
        Could also have been bad solder joints that cause the failure. Look at the joints of IC600 in this picutre:
        https://www.badcaps.net/forum/attach...8&d=1503224078
        You can see some clear ring cracks on the legs as well as the heatsink.

        While discussing the above picture... O/P, please also remove the tan/brown glue on the bottom of that PCB.

        As for recapping the PSU - I wouldn't worry about any of the output caps as they seem to be Panasonic HFQ. Those are more or less equivalent to Panasonic FC and are just as reliable. I wouldn't touch them at all. But the small L-tec and Jamicon caps, feel free to pull them and check them.

        Comment


          #24
          Re: Help identifying blown component in Dell PSU.

          Thanks Momaka thats very informative but sorry I'm no electronics genius like yourself and STJ and that a lot of that goes right over my head. I have taken some more pictures here of the little daughterboard where the IC blew and the main PCB below where its attached to.

          There are 4 wires that connect this daughterboard to the main PCB and I have been able to find out what they are for.

          Purple= goes to +5VSB on computer ATX motherboard connector
          Black= Com on ATX motherboard connector???)
          Blue= (op3) goes to block of 14 black wires on main PCB (Com maybe???)
          Brown (op4) goes to main PCB (op4) seen in centre bottom of Main PCB photo

          Two other wires disconnected (op1) & (op2), Brown & blue come from corresponding wires you can see on on main PCB

          You can see where the IC600 (subject IC) & capacitor C600 (small Taicon) cap were removed and not replaced yet

          I can see now that Per Hanson was right in it being a 5VSB board as that is the main output to the ATX connector.
          Per hanson
          If my eagle eyes are right this is a Lite-On PS-5141-2D2 Rev

          The board looks like a 5VSB board.
          I would hazard a guess that the small Taicon cap is bad and has caused this failure.
          But it could also have been a large power surge.
          No idea what the original component (IC600) was.
          But it looks easy enough to just wire in any 5VSB supply in it's place.
          Is it wired up directly to the main rectified DC voltage in the main PSU?
          And do you have that up? (Should be 155VDC with 110VAC)
          Does any of this help with a suggestion of what IC to try?
          Attached Files

          Comment


            #25
            Re: Help identifying blown component in Dell PSU.

            Originally posted by roadrash View Post
            I have taken some more pictures here of the little daughterboard where the IC blew and the main PCB below where its attached to.
            Thanks, those are quite helpful now.

            Originally posted by roadrash View Post
            There are 4 wires that connect this daughterboard to the main PCB and I have been able to find out what they are for.

            Purple= goes to +5VSB on computer ATX motherboard connector
            Black= Com on ATX motherboard connector???)
            Blue= (op3) goes to block of 14 black wires on main PCB (Com maybe???)
            Brown (op4) goes to main PCB (op4) seen in centre bottom of Main PCB photo
            Looks like the Blue (op3) and Black wires are connected to the same trace, so they are both ground. The blue wire is probably signal ground for the supervisory circuits on the secondary side of the main supply.

            Likewise, looks like Purple (5VSB output) and brown (op4) are connected together as well, so brown has 5V on it too. Most likely that brown wire carries 5V for power to the supervisory circuits on the secondary side for the main PS.

            Originally posted by roadrash View Post
            Two other wires disconnected (op1) & (op2), Brown & blue come from corresponding wires you can see on on main PCB
            Those are your 320-340V bus input/supply to the 5VSB primary side.

            Originally posted by roadrash View Post
            You can see where the IC600 (subject IC) & capacitor C600 (small Taicon) cap were removed and not replaced yet
            ...
            Does any of this help with a suggestion of what IC to try?
            Well, I tried tracing the gate/control pin of IC600, and it indeed looks like a TOP222 through TOP227 IC is what you had there originally. Thus, pick one and try it out. TOP222 were quite popular back in the day, so no harm in trying it.

            Again, just make sure to use the bulb trick I posted about above to prevent the circuit from blowing parts again, should something still be wrong.

            *EDIT*
            Oops, looks like I never posted that above. Here is a link to how to set up the incandescent bulb trick:
            https://www.badcaps.net/forum/showpo...4&postcount=70
            Last edited by momaka; 09-05-2017, 07:39 PM.

            Comment


              #26
              Re: Help identifying blown component in Dell PSU.

              The datecodes on the magnetics and PCB of that power supply are early 2001. Was the TOP221-TOP227 available then? Or might this part be of the previous generation TOP200 series, which had the same pin-out?
              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


                #27
                Re: Help identifying blown component in Dell PSU.

                Ive ordered a top222y so hope it works. At least it was quite reasonably priced at £5.95 inc delivery. when others were selling at 7.95 + delivery.
                Thanks again everyone your all so helpful . Cheers
                Last edited by roadrash; 09-13-2017, 11:20 AM.

                Comment


                  #28
                  Re: Help identifying blown component in Dell PSU.

                  shit, i could have sent you some tops for the cost of postage if i could find the bag!
                  i salvage switching psu chips from stuff i bin.

                  Comment


                    #29
                    Re: Help identifying blown component in Dell PSU.

                    Thanks for the off Stj. Your not going to believe this but while getting ready to solder in some new components that just arrived, I suddenly spotted a little black lump of silicon laying on the worktop with the number Topyai on it. It must have been wedged in the psu somewhere not easily visible. Anyway now we know what the mystery component was that blew up and you weren't very far off which is brilliant. Last question now is whether the Top222y I ordered is compatable with the original Top200yai and if so I will pop it in and test the psu.

                    Comment


                      #30
                      Re: Help identifying blown component in Dell PSU.

                      compare the datasheets.
                      Attached Files
                      Last edited by stj; 09-16-2017, 08:21 AM.

                      Comment


                        #31
                        Re: Help identifying blown component in Dell PSU.

                        page8 of the 222 pdf has a section of interest

                        Comment


                          #32
                          Re: Help identifying blown component in Dell PSU.

                          is this going to cause a issue?
                          There is no external latching shutdown function in TOPSwitch-
                          II. Otherwise, the functionality of the TOPSwitch-II devices is
                          same as that of the TOPSwitch family

                          Comment


                            #33
                            Re: Help identifying blown component in Dell PSU.

                            dont think so.

                            Comment


                              #34
                              Re: Help identifying blown component in Dell PSU.

                              I bet it's the clamp voltage is it can't be something as easy as thermal temperature. Thesee Top200yai ic's are hard to find now but I just tracked one down in case this top222y isn't compatable.

                              Comment


                                #35
                                Re: Help identifying blown component in Dell PSU.

                                the example schematics are exactly the same.

                                Comment


                                  #36
                                  Re: Help identifying blown component in Dell PSU.

                                  I did actually notice the schematics looked very similar and pin compatible but thought the spec was different. Isnt the topII a more powerful IC? than the older top?. So Its compatible then yes and do I still need the ferrite beed on it.

                                  Comment


                                    #37
                                    Re: Help identifying blown component in Dell PSU.

                                    i would put the ferrite on it - i'm surprised your holding back so much.
                                    i would have tried it before the postman reached the end of the street!

                                    Comment


                                      #38
                                      Re: Help identifying blown component in Dell PSU.

                                      Hahaha yeah done that before and Pop!. I don't have your experise. Remember i'm a motorcycle mechanic and ex radio amateur who knows basic electronics and who is trying to learn something completely new to me. Sorry but your trying here to teach a old dog new tricks.
                                      Lol.

                                      Comment


                                        #39
                                        Re: Help identifying blown component in Dell PSU.

                                        Anyway bad news its totally dead no activity in any way. Cant see any other visual defects and internal fuse isnt blown. What is the component that drives that blown Top200 PWM switch as that might be u/s as well now or any other suggestions what I should test?

                                        Comment


                                          #40
                                          Re: Help identifying blown component in Dell PSU.

                                          you have the example schematic - i know it's not exact.
                                          just meter the other parts - specially resistors.

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