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H110M-R front-usb bus delivers low current

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    H110M-R front-usb bus delivers low current

    Hi, the title describes all.

    I was a bit of an idiot and used my front-USB to power random stuff in a.... not so standard USB way and now the front ports (both USB 2.0 header and USB 3.1 header) deliver 5 volts, but so little current barely anything works.

    I have ok knowledge with electricity, and I could fix this... but I can't seem to find schematics for this board. Could anyone have it by chance :P ? If not, where would you start? Would you start at all?

    Thanks!!!!!!!!!!!!!!
    Last edited by SMDFlea; 05-30-2021, 09:03 AM. Reason: Added "H110M-R" to thread title

    #2
    Re: H611M-R front-usb bus delivers low current

    There is often a polyfuse on the USB power rail. Let it rest for a while and see if it comes back to normal. Otherwise you may have to replace it.
    There can also be a power switch IC instead of a polyfuse but that's not common on low-end boards.
    OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

    Comment


      #3
      Re: H611M-R front-usb bus delivers low current

      What is the board / product ? Zero hits with Google with 'H611M-R'.

      Open the widget and follow the wiring from the USB connector to the circuit board and continue to check the resistance of the Vbus trace (industry standard and documented on the internet for the USB 2.0 connectors.

      This should lead to some component that is in series with Vbus and is now damaged and presenting this issue.

      Comment


        #4
        Re: H611M-R front-usb bus delivers low current

        The board is H110M-R... No idea how I messed up the model that bad, but I'm guessing my head mixed up somehow because two months earlier I was working on some H61M chipset laptops... whoops

        The board has had this issue for years now and it hasn't settled. When I charge phones, they discharge faster than the board can charge them (lol) and USB drives are never read correctly.

        I'll see if I can trace the VBUS... Never worked with that before but it's a nice clue. Thanks!

        Comment


          #5
          Re: H611M-R front-usb bus delivers low current

          Update: I had a little more time to test it today, and resistance between VBUS and ground is 2.80 kilo ohms... okay so that's why there is so little current.

          Same resistance in the USB 3 header, so the same source must be screwing them up. The only thing I can do tho is set multimeter in 20k OHM mode and trace from the VBUS pin to random components to see if I can find the source (I truly hope not a chain of resistors or something is adding up to that value, otherwise it will make things complicated)

          IG it could be the polyfuse that settled down just a little... enough to let some current to pass through, hence this high resistance. Idk though, I only did some research on them yesterday when they were mentioned on the board, so is this possible?

          Any guesses as to what might be dead? When I was drawing power from bare wires, I drew a lot more current than I was supposed to (accidentally connected a resistor-less LED once even) so I'm guessing that's what killed whatever it is. If not I'll just have to try a lot until I find it, that seems plausible somewhat. An interesting thing is also how the 2.80 kOHM resistance is created slowly, rising fom 0.5 kohms to 2.80 (capacitor(s)...?)

          This would be so much easier if there were schematics
          Last edited by yuuki47; 05-30-2021, 06:18 AM.

          Comment


            #6
            Re: H110M-R front-usb bus delivers low current

            2.8khoms to ground on the 5V USB doesn't sound like a problem.

            I've already seen partially damaged polyfuse that had a few ohms across them, so you'd indeed get 5V on the USB but as soon as you start pulling a sensible amount of current the voltage collapses.
            OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

            Comment


              #7
              Re: H110M-R front-usb bus delivers low current

              Theres no schematic or boardview available for H110M-R only a repair guide, there is a boardview for the H110M-K, it might have a similar layout. The polyfuses are UF5 and UF31 .They could be marked with a P (polystar/polytronics) or LF (littlefuse) and they will have notches at both sides.
              Attached Files
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              Comment


                #8
                Re: H110M-R front-usb bus delivers low current

                Yes a bad polyfuse could be the root cause, provided there is one onboard. Technically, there should be one for each USB port. Most vendors will use the polyfuse or none at all. We reviewed many add-on host adapters from Amazon - as we were requested to design one for HP POS group - not a single adapter had current protection on the USB ports. The 'protection' will be, in this case, the thin PCB traces that will 'act like a fuse' I suppose. Nasty products in the consumer space and truly are disposable designs.

                Polyfuses are $0.05 USD or less in production volumes while a resettable electronic load switch will be $0.50 USD or similar. On an aside, we met with a large traditional fuse mfr in HK a few years ago who sampled us SMD single-time fuses for our home automation designs. Our engineer tested the current and time taken to trip the fuse - not a single one of the samples matched the datasheet. They then defended themselves that the wrong internal construction was used for the samples - resent a new batch using imported fuse wire from Germany they claimed, the new batch of fuses worked as advertised but we dropped them as a potential supplier. A single-time fuse will react faster than a polymer type but then the fuse will need to be replaced after blowing. Polymer fuses just 'heal' back to normal state but as noted, de-rate over time with the trip time, etc.

                This could be your issue.

                The LED without a resistor did not cause this fault - the polyfuses require in our opinion too much time to trip to be of any real value. The reaction time is just too slow to protect sensitive downstream electronics.

                < pix not required - thanks SMDFLEA! >

                Yes, the USB port often is fitted with a 100uf electrolytic cap to support the USB specs for in-rush current protection.

                Once known, the polyfuse can be sourced from Arrow / Mouser / Digikey - they are very common and should be < $ 1 USD in single piece qty.

                If you have the same polyfuse onboard - need to confirm the dimensions of your polyfuse but the "1812" sized component datasheet is attached.
                Attached Files
                Last edited by mon2; 05-30-2021, 10:27 AM.

                Comment


                  #9
                  Re: H110M-R front-usb bus delivers low current

                  Yeah, I did a little more probing and saw that this is normal for the board. It rises slowly so its probs just some capacitors charging, I don't think this is a pointer especially because the good usb ports display the exact same value.

                  I have spotted the polyfuses on the board, I'm not sure how to test them but I put 2M Ohm across them and they are a dead short, so they look kinda fine.

                  I measured the unloaded output as 5V, but since the current is super limited, the voltage should drop as you say. (Isn't that dangerous for phones?). It didn't because maybe the volt meter was just not enough to cause a good load.

                  I'm not sure if its possible, but will I be able to connect my volt meter in series? I'm thinking of probing around the board this way to see where the voltage drops (maybe even across the polyfuses). I really cannot think of another way to do this especially cause I don't have schematics.
                  Last edited by yuuki47; 05-30-2021, 10:30 AM.

                  Comment


                    #10
                    Re: H110M-R front-usb bus delivers low current

                    If the current is limited, the effect is like trying to start a motor with a weak battery - will be wimpy current so nothing will happen.

                    Take some pix of your board so we can compare them against what little public information is available on the net.

                    Comment


                      #11
                      Re: H110M-R front-usb bus delivers low current

                      Here are the pictures. I got as many as I could using my S9 which has a somewhat high res camera so they can be zoomed in at.
                      Attached Files

                      Comment


                        #12
                        Re: H110M-R front-usb bus delivers low current

                        Attached are the locations of your polymer fuses.

                        Did you say that EVERY USB port on your logic board is behaving the same way? That is, unable to function with simple USB widgets ?

                        Do you have a USB mouse available for testing ?

                        Dock into each and every port and confirm if it works or not. A mouse should be very low current (probably < 100mA).

                        What other USB device are you testing that does not work for you?

                        A BLACK USB insulator port = USB 2.0 and should be able to support upto 500mA (peak).

                        A BLUE USB insulator port = USB 3.0 (aka USB 3.1 Gen1) and should be able to support upto 1A (peak).

                        When you dock your phone into the port - does the phone report that it is charging ? The USB 2.0 / 3.0 port will never replace a dedicated charger because a dedicated charger can support higher currents on the Vbus rail (2.4A or higher are common). You can also test with other USB cables to rule out that the charging cable as a factor.

                        Also, when a USB port consumes too much current, the logic board should be able to sense this condition and report it as a pop-up flag - have seen that on my lab PC while testing out some early prototypes. Or perhaps the polymer fuse was considered to be sufficient for this vendor of the motherboard. It is strange if every USB port is acting in the same manner.
                        Attached Files
                        Last edited by mon2; 05-30-2021, 12:14 PM.

                        Comment


                          #13
                          Re: H110M-R front-usb bus delivers low current

                          What do those header cables plug into at the front,is there a single small pcb with the usb sockets on. What make/brand/model is the pc case .If theres a small pcb it will most likely be held in with a few screws,take it out and post some pictures
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                          Comment


                            #14
                            Re: H110M-R front-usb bus delivers low current

                            Originally posted by SMDFlea View Post
                            Theres no schematic or boardview available for H110M-R only a repair guide,
                            could you post it please?
                            i have a supposedly dead one on a shelf waiting till i can borrow a cpu to test it.

                            Comment


                              #15
                              Re: H110M-R front-usb bus delivers low current

                              Originally posted by stj View Post
                              could you post it please?
                              i have a supposedly dead one on a shelf waiting till i can borrow a cpu to test it.
                              Sorry,i havn`t got it ,and i can`t find it on any free download sites.
                              All donations to badcaps are welcome, click on this link to donate. Thanks to all supporters

                              Comment


                                #16
                                Re: H110M-R front-usb bus delivers low current

                                Hello everyone, I apologize for disappearing. I was extremely busy, but today I had a chance to look at the board again, and the schematic that was sent to me.

                                Unfortunately, the layout for the K version of this board is very different. But I had an idea: I tried to check if the ports are on some kind of different VBUS (because they have to be, right?) and they are not. Both USB2 and USB3 headers have a deadshort between their VBUS pin and the VBUS pin of the working ports, which is super confusing.

                                I suppose there could still be an inbetween component that's dead and causing a voltage drop on load (hence why my multimeter's little current passes through perfectly) so I guess the only way to firue this out is put a load (like a phone charging) and my meter in series with that. Otherwise, I'm not sure what else to do without a schematic.

                                Comment


                                  #17
                                  Re: H110M-R front-usb bus delivers low current

                                  Update:

                                  I decided to do a sanity check to see if the back USB ports do work as I think they do... so I plugged in the board simply with ATX 24-pin and CPU 4-pin... and the phone was not charging... every port was behaving in the exact same way.

                                  And that makes sense, because every positive wire in all USB ports is sorted together, so they all share VBUS.

                                  But I remembered charging my phone back when I had this board on daily use by putting in the rear ports... so like what? I felt I was gaslighting myself.

                                  And I was, because I gave the board a stick of memory to POST properly and sure enough... the board began charging the phone normally in the rear ports, but not the front ports. Like it originally was.

                                  .......................This makes no sense.

                                  I have this theory that some transistor switches the rear ports to a different VBUS when the board POSTS, maybe by something bringing up the transistor's gate to high (I don't understand this yet completely, but I do know the gist of it)

                                  And that would make sense, because when the board is not posting aka when its turned off and I do checks on it, the rear ports instead use the same VBUS as the front ports... which is why the pins are shorted together... probably through whatever transistor that is responsible for this.

                                  Of course, this is only a theory, and without a schematic I'm stuck probing random parts of the board. I found an SMD transistor (probs a MOSFET, because in the schematic of the K-variant of the board, the solder mask ID matches that exactly) with four legs. Problem is, there is no datasheet on it, and its not the same model as that in the K variant of the board. Additionally, like I mentioned, the layout for the K variant schematic is totally different, stuff are totally positioned in completely different places and the components are almost never the same as my board.

                                  But I do not think this is a problem with the MOSFET or the transistor or whatever is responsible for the switching, because then it wouldn't switch at all and worse it would just short the two VBUS lines together (sounds chaotic). Like some people suggested, this might be a trace-based fuse, maybe the line for the bad VBUS is partially blown allowing little current to pass through. It is something I could easily fix if I could just identify this trace so I can solder a wire across it and effectively fix this issue.

                                  I this this might be it.


                                  It seems to have two different 5v lines and all ports are connected to it through small caps around 850uf (according to the schematic anyway)
                                  Last edited by yuuki47; 06-12-2021, 10:01 AM. Reason: To add image.

                                  Comment


                                    #18
                                    Re: H110M-R front-usb bus delivers low current

                                    Originally posted by stj View Post
                                    could you post it please?
                                    i have a supposedly dead one on a shelf waiting till i can borrow a cpu to test it.
                                    Found it finally,and posted it in a new thread - https://www.badcaps.net/forum/showthread.php?t=96586

                                    .
                                    Last edited by SMDFlea; 06-12-2021, 01:38 PM. Reason: posted wrong link
                                    All donations to badcaps are welcome, click on this link to donate. Thanks to all supporters

                                    Comment


                                      #19
                                      Re: H110M-R front-usb bus delivers low current

                                      Originally posted by yuuki47 View Post
                                      the board began charging the phone normally in the rear ports, but not the front ports. Like it originally was.

                                      .......................This makes no sense.
                                      yes it does, the thin wires between the case connectors and the connector on the motherboard arent rated to handle more than 250mA (the original usb power spec)
                                      you probably damaged the cable or crimp connections.

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