11 Replies Latest reply on Feb 16, 2018 10:47 PM by malus_lupus

    Semi conductor failure and replacement help

    malus_lupus

      I have been checking out a power supply that failed everything looks pretty much new. However, I figured I would test components and see what crops up. Two of these semiconductors pegs short to ground all three (I cannot put anything between the do and period. I was wanting to say it of course shorts to itself. Every time I go to the end, between the period it allows a space if I am fast enough but it returns to between here. You have a bug. )do  . I was thinking of replacing them but the issue comes in the form of the 2nd number.

      The first number on these are TF14N50, I can find that no issue but the latter number I have no clue its importance it is GV5S1D and I cannot find the combo of the former and latter online. My question is what would be an apt replacement does the latter number matter? Also what would cause a failure in this component I would think it is due to overheating due to certain reasons (enough roaches poured out of one to make a man reach a pitch he should never reach especially in such a short time ) but those reasons are not apparent in another and it seems to have failed the same way it shorted out between the pegs no real ground plane to test on but they are all shorted out albeit only two are on this one so easier to do that.

      I checked the x box itself and it seems perfectly healthy so I dunno why it would cause the plugs to fail.








        • Re: Semi conductor failure and replacement help
          jw0752

          Hi Justin,

          The first number is for a 500 V 14 A MOSFET.  If you are testing these in circuit you may see conflicting readings. It might be a good idea to isolate the leads from the circuit and test them out of the circuit. the second number could be a date code or a series number. You might give us some pictures and a little more detail. These parts will some times fail for unidentified reasons. If they are really shorted you should check the power supply to them as there may also be parts in the power supply chain that have been damaged by the short. Your explanation was a little confusing so I hope I covered your question.

           

          John

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          • Re: Semi conductor failure and replacement help
            genebren

            Justin,

             

            I can not confirm for sure (as it does not show on the specification sheet) but I would bet that the markings, GV5S1D, relate to date of manufacture, lot code, place of origin, or some other code.  They are not important to your replacement.

            Good Luck,

            Gene

            • Re: Semi conductor failure and replacement help
              malus_lupus

              Here are some pics of the board. The red x denotes they are short to themselves and the thing they are screwed to which seems to be a ground plane. The .3 is what the others registered when testing them. The other pic is to show the board is relatively clean and new looking since it was (it went down there on its own) bought a few months back (and it is here now good luck reading this properly.) The other pic shows the bottom of the board besides some dull solder it is alright looking to me.

                • Re: Semi conductor failure and replacement help
                  jw0752

                  Hi Justin,

                  It is not unusual for one lead to be shorted to the heat sink. With out the board in front of me I can not say for sure but before replacing a component I would test it outside the circuit. This is usually as simple as unsoldering 2 of the leads so that they are no longer touching the traces or actually removing the component and then checking it to see if it is indeed shorted out.

                  John

                    • Re: Semi conductor failure and replacement help
                      malus_lupus

                      One yes because having a common ground plane makes thing much easier. However in the two with Xs, those have all leads shorted to ground and to each other etc. The others register ground on one lead which is, of course, proper considering the facts. I could take it out and measure it but I find it to be a pointless endeavor since all the other ones are behaving in an appropriate manner. The proper working ones measure an apt resistance from what I have read and watched of these being measured.

                      I have I think figured out why both of these failed in the same way but in different manners.

                      The one which is proper 400 volt etc had too many roaches humping it (*shudders at the flashback ).

                      The other one which is crap was very cheaply made shoddy parts and drew more voltage than it could handle. From what I looked up its component is a diode that is obsolete and is rated at 100 volts and it drew 150 volts which is oddly higher than the other plug so there may be other faults with that one. I think overheating kinda is why both of them went out. They overheated for different reasons but they did go out. I think at least from everything I have gathered thusly.



                        • Re: Semi conductor failure and replacement help
                          mcb1

                          This looks like it is a switchmode power supply.

                           

                          The overheating is usually because the capacitors on the output side age/wear out and then don't work in the manner they should.

                          You'll likely find they are low ESR versions and typically have very low hour rating.

                           

                          Leaving these plugged in just results in reducing the life expectancy, so if you can whenever not in use turn them off.

                          This also goes for cellphone chargers which are the same switchmode style design.

                           

                          While you can identify the blown transistors/FETs, you'll probably want to keep looking for the cause.

                           

                           

                          FYI Voltage is the measure of the force, while current is the amount of energy drawn.

                          It's easiest to think of two rivers, both fall the same height (voltage) and one with only a small amount of water (current) flowing through a narrow gorge/valley the other wide with a lot of water flowing.

                           

                          Cheers

                          Mark

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                            • Re: Semi conductor failure and replacement help
                              malus_lupus

                              Odd because this is an X box plug so it is supposed to be plugged in at all times for the X box. I wish I could find the cause but the caps look perfectly brand new and so on besides the hundreds of roaches in it there is no other oddities. The other one is a cheapy china one so I know the issue for that one. I have never done a conductive test on a roach but I guess it is possible a roach shorted out the cap if that is a thing is it I am unsure. I found a dead roach between the leads of the cap stuck quite well in there to be honest too well (*shivers).

                                • Re: Semi conductor failure and replacement help
                                  jw0752

                                  If you didn't see any burning the bugs probably didn't short anything out but if there were enough of them they may have acted like insulation which could have caused an over heat failure of the components.

                                   

                                  John

                                  • Re: Semi conductor failure and replacement help
                                    mcb1

                                    I found a dead roach between the leads of the cap

                                    Entirely possible it is the cause.... HOWEVER. If it was the 400v capacitor it should only affect the incoming mains.

                                     

                                     

                                    These things basically rectify the mains, with some smoothing to create 150 - 250v DC.

                                    The DC is chopped at a high frequency (100-200KHz) and feed into a transformer and that gets turned into 12/5/3v3.

                                    Feedback from one or more of the outputs controls the process.

                                     

                                    As a comparison the old analogue style simply transformed the mains to something lower and then it was rectified and filtered.

                                    The voltage was then regulated by various ways, but generally it got turned into heat.

                                    Modern switchmode supplies can be 80-90% efficient and obviously are 110 or 230v capable.

                                     

                                     

                                    Cheers

                                    Mark

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                          • Re: Semi conductor failure and replacement help
                            malus_lupus

                            Decided to desolder these things to get full readings because from what I have been reading it can be different things for different failures and the first thing I popped off was not what I thought it was it is a mystery.

                            I looked up its numbers etc nothing. The numbers and such are at the top left and right corners in circles 10, p5 and then the rest of the numbers and letters on it are BYCBX, 600p, PJA1541 B4, 9501.

                            I did some measuring.
                            In Diode mode, I registered a .392.
                            In 200k ohms resistance mode I registerd a 87.7 flucuated quite a deal.
                            In 20M mode I registered 1.57.

                            The other Semiconductors are a GDS type.

                            Anyways here is the pic.


                            (Side note not done testing the other guys yet)


                              • Re: Semi conductor failure and replacement help
                                jw0752

                                What you likely have there is a highspeed Schottky Diode. If you have an analog meter you will find it conducts in one direction and not the other. The 0.392 volt drop would be very typical of the 0.4 I would expect from a schottky diode of this type.

                                 

                                John

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                                  • Re: Semi conductor failure and replacement help
                                    malus_lupus

                                    Interesting never heard of that.

                                    The other semiconductors seem to be healthy enough. I measured at first SGDs because I looked at the data sheet but not the actual order and when I looked at the board it said the right order. So I had to remeasure them I think they are right though one may be iffy it is odd it seems okay now but it went up resistance linearly I swear once albeit that may have been when I was measuring it wrong I may have charged it not sure.

                                    These things are interesting though I still dunno why or the exact purpose in this circuitry which bugs me to no end but I know what is wrong. It is an oddity. 

                                    I have a subpar example. I sometimes am a part-time mechanic and with the car, if something is wrong I can find it and fix it but I also know the story of that part and why it is subject to failure and or more than likely that part. If a radiator needs replacing that is an obvious thing but also I know what it is for, why it is there etc and know to replace it. With circuitry I only know to fix it and how to usually and how to test if something is wrong the rest is blank and I do not like it.

                                    (Funny note all ACs are practically the same car, house, window AC etc. Just the water cycle repeating itself over and over that is it. I do not need to know that to fix one but I like knowing it etc.)