Announcement

Collapse
No announcement yet.

Replacing OST caps on Microstar KT6 Delta motherboard

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    #21
    Re: Replacing OST caps on Microstar KT6 Delta motherboard

    ta,
    upon further inspection in the daylight, the motherboard now has a pit in it, and the left pad that the cap was soldered to, is no longer there
    (have put a better photo on that webpage link)
    that vid only applies if there is two pads already there.

    i get a continuity between those two metal (they look white on the photo) bits on the left, and the motherboard earth at the metal circles around the board mounting holes

    also, i'm now going to remove the 16v and test each of them with the analogue multimeter.
    Last edited by socketa; 06-22-2014, 07:07 PM.

    Comment


      #22
      Re: Replacing OST caps on Microstar KT6 Delta motherboard

      The pad will have burned up along with the capacitor then. If you can see the track or via that it went to, you can solder the good end normally then solder the other end with a thin piece of wire. Tricky but should be doable.

      Since you have a few parts in parallel you should be easily able to find a common connection to wire to, nearby.
      "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
      -David VanHorn

      Comment


        #23
        Re: Replacing OST caps on Microstar KT6 Delta motherboard

        Ok, i can see why you're confused about what i wrote.

        When I say dc-dc converter, I generally mean to say the whole circuitry that converts a dc voltage to another dc voltage (so chip, input and output capacitors, inductors, diodes and/or mosfets etc).
        Sometimes I refer to a dc-dc converter chip or a dc-dc switching regulator and that means to me a more advanced dc-dc controller, one that often has a built-in mosfet and possibly a diode, parts that are generally required to build a dc-dc converter.
        A dc-dc controller means to me just a very basic sort of chip, in the sense that it needs those other parts to build a whole dc-dc controller. In your case, that HIP6302 is just a controller because it relies on those other two tiny driver chips to operate the mosfets, the controller just sends commands to those to increase or decrease the frequency of operation of those drivers.

        Now as you figured out, the schematic is for KT6 Delta (codename MS-6590) but there were several revisions so you have to pay attention and follow the traces to see if those part numbers match with what you have on the board.
        This being said, that tiny capacitor does look blown up and you did good by desoldering and cleaning that area.

        There's only two terminals there, one thick large pad because there's lots of current there and on the other side you may have what looks to be two traces but basically they both go in the same place.

        1. What could have caused this?

        Why did it blow up? Probably over voltage... ceramic capacitors can short if the voltage goes higher than the capacitors' rating.

        Other reasons could be just physical failure in the capacitor due to board bending, from flexing due to heat/cold cycles, from vibrations in the board from cpu cooler etc etc.

        Electrolytic capacitors rarely fail shorted or partially shorted, ceramic capacitors and tantalum capacitors usually fall like that.
        It's unlikely the electrolytic capacitors are faulty like that, but they could be out of spec.
        I would look more towards those mosfets - check for continuity between drain and source, between gate and source etc etc. If the mosfet is blown, usually the source and drain are shorted.
        Search on youtube "how to test a mosfet" .. or see these:

        https://www.youtube.com/watch?v=gloikp9t2dA
        https://www.youtube.com/watch?v=RBJGOOTEwfU
        But note this type of testing is kinda problematic when you have those mosfets in circuit, as another mosfet can affect the measurements you make.

        2. In such an instance, do those tiny caps explode before the big caps?

        Ceramic capacitors are more sensitive to over voltage. Electrolytic capacitors don't pop right away if there's some over voltage for very small periods of time, the electrolyte inside them can start to go bad, the aluminum foil can be damaged, but the capacitor will still work reasonably well.
        The electrolytics could be a tiny bit affected inside but they'll still work - they're more resilient.

        3. What is the function of these tiny caps that are in parallel with the 16v electrolytic caps, and how necessary are they?

        They're there for filtering and for EMI cleaning. Ceramic capacitors are very good at cleaning high frequency noise, electrolytic capacitors handle lower frequencies much better and do the heavy and rough work. Ceramics are for finesse, fine tuning, for decoupling .. see what decoupling means here: https://www.youtube.com/watch?v=mk61DNz27FI

        They won't be critical, you can test motherboard without them, but when you manage, you should install them on the motherboard.

        4. Does 475P/0805 mean 475 pF, and what does 0805 represent?

        0805 is the size , 0.08 inch x 0.05 inch or 2.0mm x 1.2 mm
        475p is the size. It may mean 47 and 5 zeroes after it, 4700000pF = 4.7uF. They should be X5R or X75 or C0G/NPO (temperature coefficients)
        If it's really 4.7uF, the voltage rating of the capacitors is probably as low as 10v or 16v.
        For example, it could be one similar to this: http://uk.farnell.com/kemet/c0805c47...05/dp/2409055?
        It could be even rated for 6.3v... in which case that may explain why the big capacitance value - capacitance of ceramic capacitors changes with voltage, a 4.7uF 6.3v rated ceramic capacitors may only be 3-3.5uF at 1.5v.

        5. Is it possible to solder a new cap on (with tweezers and an electron microscope)?

        It is possible but it may be very hard because one of the traces is a large copper pad which will suck up the heat from your iron tip.
        After cleaning up the burned area and the disintegrated cap,

        i turned the board over and tested [...]

        Not sure how you used the multimeter... but you should know that you really can't get accurate results because all those capacitors are in parallel on the board.
        You get the capacitance that's basically the sum of all the capacitors, you get a much lower ESR value that's also affected by those smd capacitors.
        Really, you can't test capacitors in-circuit, if they look bad or swollen you would replace those anyway.

        If you don't have an ESR meter, you should know that capacitors can go bad and still show good capacitance because multimeters measure the capacitance at low frequencies. The characteristics of a capacitor change when it's working at 100kHz or whatever frequency they're subjected to when motherboard works, that's when the ESR value changes and the circuit can go bad. So if you're not sure about them, just replace them, it's safer.

        Comment


          #24
          Re: Replacing OST caps on Microstar KT6 Delta motherboard

          Thanks again,
          That's some seriously good info.
          i note the two phases on the same mosfet (the two separate drawings on the schematic caught me out for bit)
          will be revisiting those first two vids for a recap-itulation.
          before i do, just quicky...
          1. The "HIP6302 dc-dc converter", that you mentioned, is the PWM?
          And the "phase controllers HIP6602" is one component containing two drivers/doublers.
          So, looking at the schematic, the current is coming in, getting smoothed by the capacitors, then going into the drivers, and then into the PWM!
          But the dude in the video says that current hits the phase controller, and then goes to the drivers/doublers.
          2. So is the reason why the current goes to the drivers first - because this is for the feedback loop?

          Regarding that meter reading (which indicated continuity), when placed across any of those 12v, or 6.3v, electrolytic caps before the mofsets:
          I grabbed another board that was good, and got the same results
          So this continuity appears to be normal
          Used the digital multimeter ohms beeper and got continuity, when probes were placed across the 6.3v caps, and a brief beep when across the 12v
          Which is the same result as for the faulty board

          Seems that some current is allowed to flow to earth via those transistors (Q27-Q30), or then through the mofsets, to earth, since the multimeter shows complete continuity or (in the case of the 12v caps) some non-infinite resistance?
          Thinking about it now, it seems makes sense - even obvious?

          On a separate note,
          i'm beginning to wonder if that melted cap, although it looked split in half, was actually a slight short, and therefore not enough current was being supplied to the PWM for the CPU to fire up (should have tested that before cleaning it).
          When i tried a good cpu, a week ago, the CPU was cold, but the CPU fan was spinning and it stopped and started once, before i turned off the power.
          Last edited by socketa; 06-22-2014, 11:36 PM.

          Comment


            #25
            Re: Replacing OST caps on Microstar KT6 Delta motherboard

            HIP6302 :

            Microprocessor CORE Voltage Regulator Multi-Phase Buck PWM Controller

            The HIP6302 multi-phase PWM control IC together with its companion gate drivers, the HIP6601, HIP6602 or HIP6603 and Intersil MOSFETs provides a precision voltage regulation system for advanced microprocessors.

            -
            Don't look at the board and think it's layed out exactly as in the schematic. 12v doesn't have to go into the controller, come out and go somewhere else, they're not in "chain" - the controller 6302 and the drivers 6602 can be somewhere further away from the mosfets and capacitors and some tiny traces can send 12v to them to power them up and other tiny traces can go to the mosfets and drivers and so on.

            -

            The continuity mode on your meter will beep at low resistance (varies from meter to meter, can be anything less than 10 ohm for example).
            Just tested on an old board I have around, used continuity mode over one of those capacitors by the cpu, i got 6.28 ohm. You're not supposed to have no resistance and it doesn't tell you the capacitor is shorted, it just means there's something in parallel with the capacitor making the multimeter think there's continuity.


            I have to get some sleep now, won't reply for at least 8-10 hours.

            Comment


              #26
              Re: Replacing OST caps on Microstar KT6 Delta motherboard

              That's cool, when/if ever you want
              no problem

              Regarding the VRM, in terms of the direction of current flow.
              The way you describe it in post #17: PSU > 4pin12v > 16v caps > 4 mosfets
              The guy in the vid says: PWM > Driver/Doubler/ > 4 mosfets > 2 Phases > inductors > CPU
              So you might see where i was getting confused?

              i now note that there is two terminals on the scematic called VCC - one at the top left, and another at pin 16 of the PWM.
              And also see that the label VCC can refer to one physical terminal with at least these two circuits connected to it.
              so i can now see that current flows forward in both of the above descriptions.
              is the path that you describe the feedback loop?

              Anyway, still have to rewatch those two vids again, and the mofset ones

              Powered up the Mobo again, just to see if it would boot, since the melted cap is now removed.
              Nope - only CPU fan spins
              Both pins show 12v on the multimeter, and the earth pins are good also.
              When i pull out the 4pin connector, i can hear the PSU fan speed up,
              which, to me, suggests that current is passing through the VRM (when the 4pin connector is plugged in).

              off to get some zzzzzzzzzzzzzzzz's now also.
              Last edited by socketa; 06-23-2014, 05:04 AM.

              Comment


                #27
                Re: Replacing OST caps on Microstar KT6 Delta motherboard

                I don't see how it's so hard to understand. We're talking about two different things.

                The thick, heavy current flow goes like this :

                12v > input inductor > input capacitors > mosfets > output inductor > output capacitors

                The mosfets are like on/off switches that have to be turned on or off by something. No matter what state the mosfets are in, you still have 12v after the input capacitors.

                So after the input capacitors, a bit of 12v is taken to power up the controller and drivers which then turn on or off the mosfets and monitor the output voltage and adjust how fast the mosfets are turned on or off to maintain the voltage where desired.
                The heavy current, the amps on 12v, don't go through these controller+drivers side, for example in theory they could be powered separately from a 9v battery if you'd want to... they just take power to work from the same 12v because it was convenient, already there close to the chips.

                So you also have

                12v > input inductor > input capacitors > controller (and )
                12v > input inductor > input capacitors > driver(s)

                and then you have signals like this:

                controller ----> drivers ----> mosfets (on/off)

                At any time, there's 12v at the input of the mosfets, controller and driver but without signal from the drivers, there's no output voltage on the mosfets, they're switches after all controlled by the drivers.

                So I'm talking about how current flows from input to output looking at the controller/driver as something auxiliary, as a sort of "management" circuitry, a "gatekeeper", which just controls the flow.

                He's arranging the components in the order of importance, not in the order the components are physically connected on the board. He's basically saying:
                First is 12v, inductors and capacitors because nothing works without it.
                Next is the controller and the phase drivers because mosfets depend on them to work, without them nothing moves further in the circuit.
                Next he puts the mosfets because those let the current flow through them, if they're dead or don't turn on or off, current doesn't flow further.
                Next is the output inductor which smooths the current pulses and the output capacitors which further smooth things out.

                Comment


                  #28
                  Re: Replacing OST caps on Microstar KT6 Delta motherboard

                  OK i get it.
                  A lot clearer now, thanks.
                  Just 2 little questions about that:
                  1. "after the input capacitors", the tee off that feeds the controller is not shown on the schematic. Is this the "VCC" terminal 16 on the PWM (HIP6302)?
                  2. i see that terminals 13 and 8 (Phase 1 & Phase 2) on the driver (HIP6602), go straight to VCORE, what is the function of this path? - It looks like they tweak the thick heavy current that suppies the CPU.

                  I'm not too keen on desoldering the mosfets if it's not absolutely necessary.
                  So, i powered up the motherboard (with known good ram and CPU),
                  then checked voltage at mosfets Q28 and Q30 - the Drain shows 12.2v and the Source shows 1.62V - which looks like the right voltage to power-up the CPU
                  3. (BTW, what is the function of the other two mosfets (Q27, Q29)? - when they are switched on, they look like they create a path to earth)

                  Seeing 1.26V on the Source of Q28 and 30, rules out the possibility that these mosfets are shorted between Drain and Sink

                  So seeing that the voltage was correct at the source of both mosfets (which seems to indicate that the PWM is doing that part of it job correctly),
                  i then tested both sides of both of the chokes, and got 1.62V there.

                  4. i also note that there is another path to the VCORE terminal, that comes from the PWM terminal (VSEN) - what does that do - is it a sensor?

                  Anyway, what would be the next logical step after this testing?
                  Would it be to remove and test the (some of which are) very slightly bloated 6.3v output caps to make sure that they are not metamorphizing into resistors, or is there a way to go straight to the VCORE terminals (or are they hidden under the CPU housing?) and test voltage there before removing and testing the suspect caps?

                  Cheers
                  Last edited by socketa; 06-23-2014, 08:16 PM.

                  Comment


                    #29
                    Re: Replacing OST caps on Microstar KT6 Delta motherboard

                    Edit (for clarity):
                    "Seeing 1.26V on the Source of Q28 and 30, rules out the possibility that these [other two mosfets] are shorted between Drain and Sink".

                    --------------------

                    There are 2 ceramic caps before the choke, a 1uf and 0.3uf.
                    then after the choke, are the elecrolytics (the bulk capacitors?).
                    then, after that, there 2 more ceramic caps, which are 4.7uf (475P)
                    Would all of these 4 smaller ceramics be decoupling capacitors? (the guy in that decoupling capacitor vid suggested that the first one would be a bulk one, but i don't think so in this instance)


                    Looked up what the P meant http://www.wescomponents.com/datasheets/capacitor/ and it appears that it is tolerance (+100% -0%)
                    On this webpage: http://au.rs-online.com/web/c/passiv...ved=4294519046 there isn't any with that tolerance.
                    Would another one of them do the job?
                    There is one that is (-20, +80), but that is a Y5V - not an X5R, or X75.

                    Comment


                      #30
                      Re: Replacing OST caps on Microstar KT6 Delta motherboard

                      I've explained already the above.

                      p is short for PICOFARADS

                      475 means 47 x 10 ^5 = 47 x 100000 pF = 4,700,000 pF = 4700 nF = 4.7 uF

                      It's not necessarily for decoupling, could be for a similar role, to reduce EMI (electromagnetic interference) and make the motherboard radiate less "noise".

                      You'll never see y5v capacitors on a motherboard, look for X*R.

                      Comment


                        #31
                        Re: Replacing OST caps on Microstar KT6 Delta motherboard

                        Test results:

                        Removed all 6.3v caps, and un-soldered the D&S legs of the 4 mosfets

                        Tested the (removed) 6.3 caps on ohms X 100 - needle rose, then slowly fell right back down - indicating charging up, then eventually no current flow.


                        Mosfets test, DMM readings (as in the quick & dirty mosfet testing vid)
                        All of them turn on and off:

                        These two mosfets switch current to chokes
                        Q28 = 0.044v
                        Q30 = 0.021v

                        These two mosfets (different types from the above) had source connected to ground
                        Q27 = 0.478
                        Q29 = 0.514

                        all mosfets have diode reading of about 0.5V

                        with the 12v input caps left in (not yet removed) , the meter shows a partial short across their rails,
                        so that seems to indicate a fault on the input side, because the mosfet drains are physically disconnected, and the only path for current reach earth, is via one of those caps.

                        am wondering if that other little 4.7uf ceramic is on it's way out (even though it looks OK), since it is reasonably close to the other one that got fried.
                        Last edited by socketa; 06-26-2014, 06:23 PM.

                        Comment


                          #32
                          Re: Replacing OST caps on Microstar KT6 Delta motherboard

                          Ok
                          Trying this:

                          There is a contact to ground ("0 ohm", in the picture below), that i'm thinking should not be present.

                          At the bottom of this post is a diagram of the current situation.
                          i have erased the parts of the circuit that are disconnected (at the fets) and where components have being removed (the 6v caps and the choke)

                          Can someone please confirm that the problem has to be a faulty HIP6602 driver earthing when it shouldn't,
                          (downloaded the diagram of the driver, and note a couple of spots where it could possibly short circuit)

                          or back beyond the driver, towards the PWM,

                          or a fault into the vcore terminal (on the right side of the diagram).

                          Should i remove the choke to prove which way the fault is?

                          (i broke the other choke, trying to wiggle it out - so, discovered that they are reasonably easy to break)


                          (had to post this jpg inline, because the gif that i attached got re-sized too small)
                          Attached Files
                          Last edited by socketa; 07-01-2014, 11:06 PM. Reason: gif got resized too small, but jpeg got through OK

                          Comment


                            #33
                            Re: Replacing OST caps on Microstar KT6 Delta motherboard

                            Driver could be shorted, or something that rail is powering. What is the DC resistance of the choke itself? You may be able to find which side of the choke the short is on by measuring both sides of the choke with respect to ground, and the side with the lower reading will be the side with the short (since the other side will be measuring with the choke in series with the short)

                            Depends on the choke resistance and the sensitivity of your meter, though.
                            "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
                            -David VanHorn

                            Comment


                              #34
                              Re: Replacing OST caps on Microstar KT6 Delta motherboard

                              no difference in readings

                              can't see how a choke such as this would introduce any noticeable DC resistance - pretty thick copper wire.

                              did post a good inline picture but it vanished, and there is only a 30kb one when the thumbnail is clicked on - which is way too small

                              will try again now
                              Attached Files

                              Comment


                                #35
                                Re: Replacing OST caps on Microstar KT6 Delta motherboard

                                Yeah I didn't think it was likely to, but it's one way to help narrow down where a short might be.

                                You will probably have to remove it instead then

                                This is assuming of course that your board uses the exact same schematic as that reference one you posted.
                                "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
                                -David VanHorn

                                Comment


                                  #36
                                  Re: Replacing OST caps on Microstar KT6 Delta motherboard

                                  To keep things simple, let's do this one step at a time...

                                  Have the bulged Ost caps around the CPU been replaced already? If not, replace them along with any other suspicious Ost and Teapo caps and then test the motherboard.

                                  If it works, good. If not, then we go back to testing. I see the CPU VRM is spitting out about 1.6V, so it's probably working fine.

                                  As far as the shorted ceramic cap you removed – don’t bother with a replacement if the traces on the board are burned. Just clean up the area as much as possible to remove any short circuit paths (carbon dust is a good conductor, so if the PCB is burned, scrape away as much as you can with a small screw driver or some other small sharp tool).

                                  CPU VRM is a bit tricky to test, but nothing too complicated. Yes, it's normal to have half of the MOSFETs have their Sources connected to ground and their Drains connected to the inductors (i.e. CPU V_core rail). These are usually referred as the "lower" MOSFETs. The "upper" MOSFETs have their Sources connected to the inductors and their Drains connected to 12V.

                                  With a CPU in the board, the lower MOSFETs will almost always appear as shorted, so this is normal. Without CPU, you should get a fairly high resistance (few hundred of Ohms or higher) or open circuit. However, some motherboards (very few actually) also have their Northbridge draw power from the CPU V_core rail, so even with the CPU removed, you may still get a low resistance reading. Looking at the pictures for this board, I don't see a separate buck circuit for the Northbridge, so it is possible this is one of those few boards that powers its Northbridge from the CPU V_core rail. Therefore, don't be alarmed if the "lower" MOSFETs appear shorted even with the CPU removed.
                                  Last edited by momaka; 07-03-2014, 01:09 PM.

                                  Comment


                                    #37
                                    Re: Replacing OST caps on Microstar KT6 Delta motherboard

                                    thanks for the reply,

                                    OK,
                                    The CPU is removed, and still hard short to ground (0 ohms)

                                    Comment


                                      #38
                                      Re: Replacing OST caps on Microstar KT6 Delta motherboard

                                      Try the recap still.

                                      Worst case scenario is that even if nothing works and you if don't get the board running no matter what, you can still pull your new caps out and put them on a new board or some other device that needs new caps.

                                      Comment


                                        #39
                                        Re: Replacing OST caps on Microstar KT6 Delta motherboard

                                        OK,
                                        will be using panasonic FM range,
                                        and will revive this thread when it happens

                                        but after destroying the other board, the priority now is sorting out a couple of decent PSU's

                                        Comment


                                          #40
                                          Re: Replacing OST caps on Microstar KT6 Delta motherboard

                                          Can someone please help me find a replacement output choke and a couple of mosfets since i'm getting ready to make an order for parts

                                          (reason for replacing these parts is that i broke the choke and the mosfets have diode readings of 0.034v and 0.072v, on diode test mode)

                                          i can't find any replacement choke
                                          HERE, that is 1.1uF / 25A
                                          (although there is lots of toroidal inductors that look like it)

                                          The choke is labelled on the vrm schematic as 1.1uH / 25A

                                          Both mosfets have this printed on them:
                                          D432AN
                                          FDB
                                          6670AL
                                          i think that it is a fairchild mosfet

                                          So, would it be OK to use THIS,
                                          as, in the component description, there is a note saying that this is a replacement for it.
                                          Attached Files
                                          Last edited by socketa; 08-11-2014, 03:42 PM.

                                          Comment

                                          Working...
                                          X