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Current / voltage injection don’t work for me.

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    Current / voltage injection don’t work for me.

    Hello, I recently use PSU for voltage injection. I sent 1.2v 5A in big MSI motherboard and I felt nothing geting warm with my fingers (don't have termal camera). Finally chipset is dead (saw by using meter).

    So voltage injection don't work, but it's big gamer laptop MB so, why not. But I used voltage injection again for small Asus Zenbook lapotp (14'). 1.5v 5A and I felt nothing again. Probably CPU/chipset dead because caps at reverse side are shorted to ground (0 Ohms) but I felt no warm. I used thermal probe and temps grew up for 4 degree C. Low for 7.5W ?

    What's happen ? My PSU is bad ? Wich values do you use for voltage injection pls ?

    Re: Current / voltage injection don't work for me.


    What happen on your power supply when you inject voltage? What is the current value it is 5A?
    If you have a small cap shorted it can be difficult to detect heat with your finger or thermal probe. You can use freeze spray to detect heat.


      Re: Current / voltage injection don't work for me.

      If I inject voltage, I do not inject more voltage than the rail is rated for. If you are on a 3.3V rail, inject no more than 3.3V. As or the current, it depends again. Start with 1A but usually I don't use more than 5A. Once I injected lets say 3.3V at 3A, with my variable CC/CV lab power supply and can't feel any heat after a minute, I put 99% rubbing alcohol on the board. When a component starts to bubble, it's your candidate. This trick never let me down, providing there is a shorted component. If there is an open component, this voltage injection / alcohol trick does not work, because no current is drawn.


        Re: Current / voltage injection don't work for me.

        When I put the probes, PSU fan spinning and the display grow up from 0 to 5 amp and voltage down from 1.5 to 1.2v.
        So I guess PSU works and there is not open circuit.

        Ok for same voltage as rail, but in this case, some caps on, and under chipsets are shorted to ground, so protections to overvoltage could be down and destroy chip. (But I will probably do that in last try).
        For a small component, I agree, that could be hard to fell but I supposed after 1-2 min, the heat expand in zone around and can be easy to feel. But I was probably wrong, I will try again.


          Re: Current / voltage injection don't work for me.

          whatever you do, do not exceed the voltage supposed to be on that rail. 5A is quite a bit of heat to dissipate, so something must be getting hot somewhere. If a shorted rail is drawing current, it's going to go up in heat.
          BTW how much resistance are you reading with your Ohm meter?


            Re: Current / voltage injection don't work for me.

            0 Ohms, true shorts.
            PSU seems faulty, probes in serial, I measured 0.4 Amps max while I increased from 0 to 5 Amps (displayed on PSU). It’s new PSU, I used it 1 time before and it provided 5 Amps… ?


              Re: Current / voltage injection don't work for me.

              Originally posted by corrize View Post
              (...) PSU seems faulty (....)
              Not necessarily, it might be auto shutting down due to overload. You will need a higher power rated PSU.
              Inspect visually the MB, search for damages, most likely caused by those massive cooling heat sinks. Remove all components from sockets.
              Last edited by megaraider; 12-17-2021, 04:36 PM.


                Re: Current / voltage injection don't work for me.

                What is the make/model of the power supply you are using?


                  Re: Current / voltage injection don't work for me.

                  Thanks, bad measure last time, the new measure show the PSU works.
                  The model is : QW-MS305D, bad one but only for current injection, that should do the job I thinks.
                  )works. The MSI board is nude, heatsink removed, all connectors removed.
                  New try with 3.3v, 5 Amps and the same : the board keep cold. I inject at the 3v coil after 3.3-5v chip. I tryed alcohol around mosfets close to the coil, around a big cap and (and chipset), all shorted and nothing is hot. Same around 3-5v chip. And thermal probe measure only 3 degree C in addition on these zones.
                  I tryed with a thin wire for inject current and it get hot. But the board keep cold. I checked again tfor short in connectors (USB, HDMI…) and found nothing.


                    Re: Current / voltage injection don't work for me.

                    Forgot to mention:
                    desktop motherboards, because easy accessed, are prone to misuse, people keep exchange modules. Inspect with a magnifying lens all sockets (RAM, PCIe, ...), search for bend / wring pins inside. It's the most likely cause for such a strong power rail short.


                      Re: Current / voltage injection don't work for me.

                      I tryed again, with my lips everywhere on the board, with thermal probe and the MB (laptop) keep cold everywhere.
                      On the big chips (CPU, GPU, chipset) ; cold. Same temp.
                      I checked again with amp meter and 5 amps measured. I feel the wire of meter hot, and nothing else.
                      I changed place of injection probe, same result.
                      I checked all the connectors (except ram slots but visual inspection is perfect), no bent pin, no short to ground, all pins at ground are ground on boardview. The MB look like new.
                      I don’t understand how to such power can disapear. I make a short breake with this board and I will try again with the zenbook MB, a small card.


                        Re: Current / voltage injection don't work for me.

                        Update : current injection works on the Zenbook small board, but I feel a very very low hot spot with my lips under the die of chipset. Hard to feel. With 1.2v-5A and pre heat on room’s radiator.
                        That seems a very low result for such power sent. Maybe PSU don’t provide all power displayed when it is shorted. I measured 5 amps with amp meter but no idea of true voltage.
                        I will back to the MSI board. But now I see the PSU as not enought for such big gamer card. I checked again connectors and all is OK. I’me pretty sure there is a faulty component (or chipset)
                        On this board, only one coil is shorted : 3v (of 3-5v chip). Previously, I sent 3.3v 5amps on this rail and nothing was hot. How can I increase power ? Increase voltage a bit ? Inject on another rail . 1v direct on chipset ?
                        19v rail is not shorted but some caps on chipset are shorted (0 Ohms to ground).


                          Re: Current / voltage injection don't work for me.

                          Originally posted by corrize View Post
                          On this board, only one coil is shorted : 3v (of 3-5v chip). Previously, I sent 3.3v 5amps on this rail and nothing was hot. How can I increase power ? Increase voltage a bit ?
                          Stick to this rule!:
                          Originally posted by CapLeaker View Post
                          whatever you do, do not exceed the voltage supposed to be on that rail.
                          First identify the shorted power rail. Then stick to the above rule for current injection.
                          Keep in mind that all components (caps, etc) connected directly to this power rail will seem to be shorted!
                          If your PSU doesn't supply enough current use an higher rated one.

                          [Keep in mind that coils are nothing more than copper wire, thus when measured they have a very, very, low resistance value. When bad most often they are open, not shorted as they seem.]


                            Re: Current / voltage injection don't work for me.

                            Yes, thanks, I know that. I made 2 years of electronic school, I have some basis. But for repair, I have no experience.

                            I think i can deduce too, PSU is not enought. I search on the forum, some advises from experience. I guess some people on the forum has already diagnose such big boards and used more than 3.3v-5A for find a short. I would like their opinions.

                            I deduced too the chipset is dead. Because caps are shorted to ground on it, and because I don't felt any hot spot the board while I felt the thin wire of PSU hot. So there is not a very small component horted on the board, otherwise I would have felt it. And after check all connectors, the only one component left able to take such heat without feeling anything is a big chip, so chipset. I just wanted a confirmation that the PSU can't gave.
                            thought too it's maybe possible to plug the charger (19v is not shorted) in addition to the current injection for increase power. Someone has already do that ?


                              Re: Current / voltage injection don't work for me.

                              Don't mess with the charge adapter. Most likely you'll burn the power regulators and Mosfets on board!
                              Any decent rescued ATX power supply will provide 3.3V@20A output. More than enough...