Question Find a short to Ground on Nintendo Switch Motherboard

Discussion in 'Switch - Exploits, Custom Firmwares & Soft Mods' started by ZetShock, Jan 28, 2018.

  1. ZetShock
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    ZetShock Member

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    Dec 14, 2017
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    So its been a while since I last posted something similar, and I have yet again to return to this forum about a repair question for a Switch I am currently repairing for a relative.

    Anyways, the consoler does not turn on nor does it give any signs of life off of it. Plugging in the battery or a charging cable results in a faint high pitched noise from the mainboard (that usually can be heard when the console is fully functional and running), which suggests the motherboard does receive power. As it appears to be, after comparing the motherboard of a functional Switch against this one, is that on the faulty board, a 1,8V power line is shorted to Ground through a component that I am trying to find. Powering that 1.8V rail with a lab bench power supply results that on the faulty board around 0.4 Amps of power is running through the rail to ground, and measuring the resistance between that power rail to ground shows that we only have a resistance of about 3,4Ω between those lines.

    When calculating the wattage that this power loss is occuring at, we get around 0.7 Watts of power loss, which is barely heating up the component that is shorted, yet because of the short of those two rails the processor, and all caps/resistors that are near the processor on the opposite side of the board dont get the full 1,8 Volts they are supposed to get, hence why the console does not turn on or do anything at all.

    Since we are dealing with a short here, one could assume that the area of the short heats up, but using the freeze spray or alcohol method to see what area evaporates first did not bring any results, as about 1 Watt of power loss in that area is not providing enough noticeable heat. So, since we cannot use heat to find the fault, how else could I possibly find a short? I have known locations where to measure the 1,8V lines, but as well all know we cant accurately measure if a component is shorted while it is still soldered into place.

    I have attached a cutout of the back of the mainboard where the short is most likely to be.

    Now, I know this is not a technicians forum, but perhaps one of you guys might have an idea. And of course, feel free to ask me any questions regarding the motherboard or what Ive tried already.

    Thanks in advance!
     

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  2. Kerbangman

    Kerbangman GBAtemp Fan

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    Sep 19, 2016
    Thats a hard one to sort without taking components off.

    I would first check for ESD protection devices on the rail.
    Possible static attack and a TVS etc pulling the reg down.

    Check the regs by lifting the output pin to see if the rail lifts.

    Ceramic caps tend to be reliable.
     
  3. isoboy
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  5. JacksonS

    JacksonS GBAtemp Fan

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    I doubt there's just a random passive component causing a short to ground. The IC that produces 1.8V is likely damaged and needs to be replaced, or any other ICs that interface directly with the 1.8V rail.
     
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  8. linkinworm

    linkinworm GBAtemp Maniac

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    you really want to just buy a multimeter and find it properly, you cant just guess this stuff, everything leads to somewhere and you can find the component causing the issue fairly quickly, even a cheap one that just beeps might be enough to just find thing out, ideally you get one that can at least tell if something is drawing too much voltage or not enough voltage when it should be
     
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  11. snam11

    snam11 Member

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    well, i would use the simplest way to check if one of the caps is shorted: with a multimeter with the continuity mode (or if yours have it, set it with the "beep" sound on), use the probes on both sides of the cap.
    if you hear a sound, the cap is shorted and needs to be replaced. If all the caps are ok, i'm out of clues
     
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  12. Bladexdsl
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  13. FAST6191

    FAST6191 Techromancer

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    What is with the spam and dumb cunt responses? Do we want another 3ds or wii section? It will happen again if you all drive off people with genuine questions. There are doubtless places on the internet with a higher proportion of fault finding types or relatively more active ones but it is hardly absent here (games, modding and such not being unknown hobbies among said electrical repair inclined types) and it is not a new phenomenon either.

    That picture I can't do much with as it is far too low res -- it is possible to do with a camera but microscope or loupe is what I would have to play with. Nothing there looks obviously misaligned, badly placed or big solder blob shorted but at the sizes and lack of res there I am very far from any kind of certainty.
    Compared to the switch teardown on
    https://www.ifixit.com/Teardown/Nintendo+Switch+Teardown/78263
    You appear to be missing a component in line with the top of Z in the stamped alphanumeric bit. Whether that is a simple hardware revision or not I do not know but I mention it anyway. Can't tell what it is on that but a little black band device could well be a power supply of some form and thus causing a low voltage in that location in its absence. Picture is too low res to see if it was a mechanical removal or something, not that a bad day with the paste dispenser would show even then.

    Anyway I assume no thermal camera -- 0.7 watts is not a lot (might even struggle with fingers outside of a known fault/common fault scenario) but most surface mount components are rated for less than half that (maybe even a quarter that) and will thus cause them to light up rather brightly under said thing. IR thermometer might do too but it will take longer. I should also say it is not impossible that initial current draw is rather high (it is an underclocked shield after all, if said clocks or multipliers thereof are software set...) and it is then reduced by whatever means, if the thing is stuck in a boot loop and can not get to the current drop part then this may be a red herring. If you have a known working reference then that might be worth testing against.

    Cowboy method. Fly a voltage lead to different points in the chain to narrow the fault down further. Normally better to save that for open circuit faults but can do things here. If you want to create more work you can also try breaking ground connections and providing them back.

    Have you tried light pressure on/flexing of the board? For these multi layer monstrosities then it can tell you a surprising amount.
     
  14. Rauliki

    Rauliki GBAtemp Regular

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    Oct 24, 2016
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    If you have a working switch board you can measure all resistance, check capacitors, voltage and compare.
     
  15. FAST6191

    FAST6191 Techromancer

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    Measuring things in circuit is tricky, as the OP mentioned. Or if you prefer
    https://xkcd.com/356/
    Even with a reference the rest of the system may be different enough to really mess your readings up. Good enough for checking for a dead short or for something gone open/several orders of magnitude different.

    You can desolder one leg but that is a lot of work, or maybe do something with high frequency if you have it but then you have to interpret it.
     
  16. B4rtj4h

    B4rtj4h Gaming addict #2 and some

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    This is so interesting to follow! I use a very inconvenient way to see if there is a short... us an LED.
    When connecting the pins between the LED it should light up.
     
  17. ZetShock
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    ZetShock Member

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    Dec 14, 2017
    Germany
    The problem is that when measuring any cap on that power rail you always hear beeping, because you cannot know whether the short is across the cap you are measuring on or if it is across somewhere else, and the cap you are measuring on is connected to that shorted component.

    Tried that already, but thanks anyways!

    — Posts automatically merged - Please don't double post! —

    Of course it is always possible to desolder all of the components on the back, but they are extremely tiny, and even though I can do micro soldering it would be alot of work. Dont have an oscilloscope, so cant interpret any signals :/
     
  18. ZetShock
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    ZetShock Member

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    Thanks for the detailed suggestions! Anyways, the picture I provided is a reference picture, and not from the board I have. If needed I could post higher resolution pictures of both motherboards from a working and the faulty console. Ill perhaps try flexing the board, but I do not believe that the short is caused by traces touching internally in the PCB. Breaking ground connections is something I could try, but again, we are dealing with lots of small components here, and hot air soldering them off and on one by one will probably break the board once I find the fault. Comparing a working board against this defective board visually, as well as any resistance/voltages did not give me many results so far, except that we know that I have a low resistance from a power line to ground, whereas on my working board I would get multiple thousands of ohms of resistance, so there definitely is something at fault here.

    Ill inspect the board further, perhaps I can find anything interesting.
     
  19. Selver

    Selver 13,5,1,14,9,14,7,12,5,19,19

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    Dec 22, 2015
    Since the switch came out less than one year ago, and came with a 1 year warranty, it seems "obvious" to ask... why not have the unit repaired under warranty?

    FAST6191 also mentioned something interesting:
    At the risk of asking the obvious, have you validated the connectivity of the system's eMMC daughterboard? If it's stuck in a boot loop, it may be unable to decrypt / validate the boot signatures needed, or perhaps doesn't even see the eMMC device at all?
     
  20. LineoftheDead

    LineoftheDead Advanced Member

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    Oct 24, 2015
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    welcome back dude - you mentioned 3 - 4 ohms to ground and a probable short, when testing a good unit, what ohm reading do you get?

    the only reason I ask is because I was banging my head against a wall for a similar situation with yet another product (not a switch). 1.8v rail went to +1.8v rail via jumper. component just before +1.8v rail was boiling hot. clearing jumper stops that from boiling. checking +1.8v with jumper removed shows little resistance to ground (this rail goes to video chip). I removed every component on +1.8v rail (most of them are 0 ohm resistors and only one way to ground via capacitor (which tested OK)), but no change in ohms. I then moved backwards, the IC that was getting hot was receiving 3 volts on input and sending 3 volts to output pin. 3 components before this IC is a voltage divider, (like a series of resistors). this voltage divider should be taking 3 volts and changing that to 1.8 volts.

    I did solder a wire directly to ground and to +1.8v but nothing had gotten hot... probing verified voltage was correct.... voltage divider is the issue, unit was being supplied 3 volts on a 1.8 volt rail

    I guess what im getting at is.... you might not have a short to ground. test voltage to ground on both units and report back. look up any part numbers you can find on IC's and test both input and output pins
     
  21. cyris69

    cyris69 Member

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    maybe try the alcohol method to locate the shorted/bad component?
     
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  22. ZetShock
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    ZetShock Member

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    Dec 14, 2017
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    I did not yet, but that would not explain why there is a low resistance on the faulty board whereas there is a high resistance on the working board between the power rail and ground

    — Posts automatically merged - Please don't double post! —

    I even tried freeze spray, but the little current that is running through the short is barely heating up anything. Ill give that another try, but I doubt it

    — Posts automatically merged - Please don't double post! —


    Great to see you on here again! Right, so it would make sense to find the area where these 1,8v are being made, which is probably through a voltage divider as you said. Some ICs I could find datasheets for barely show any information as to what pin is supposed to receive what voltage, but I do have a couple of locations that I could check if any measurements exceed the maximum rated voltage for that component. I will measure the resistance between the rails on the working board later today and post an update.

    Also, since I recently got myself a lab bench power supply, and if the problem is indeed a component shorting something to ground, I could hook up the power supply to the 1,8v rail and ground to see how many amps are flowing. In fact, I tried this before to heat up the area that was causing the short and to find it with the alcohol method, but the produced heat was just to little to be noticeable. Though, increasing the voltage on the power supply above 1,8v to heat up and identify the faulty component easier should in theory work, right? If we are dealing with a short here a higher voltage should not damage any other components on that rail that are perhaps only rated for a max of 1,8v because the power is running through the short. Im just afraid to burn any traces on the pcb, so perhaps this is only the last thing I should try before everything else.
     
  23. LineoftheDead

    LineoftheDead Advanced Member

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    be careful, its 1.8 for a reason, raise the voltage and you risk blowing the entire rail (what if you blow video?)
     
  24. 51mmz0rz

    51mmz0rz Member

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  25. TiMeBoMb4u2

    TiMeBoMb4u2 GBAtemp Advanced Maniac

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    Although I'm not sure if he is willing to delve into it, "Hector Martin (marcan42)" seems to love tinkering with these types of issues.
    Here's his Twitter: https://twitter.com/marcan42
     
  26. citrus3000psi

    citrus3000psi Member

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    You can trace shorts down with an ECR meter.
     
  27. FAST6191

    FAST6191 Techromancer

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    Would someone without a scope have such a toy? Unless you mean one of those cheap component testers that seem to be popular nowadays.