The Little Replacement PSU That Could: Kill A Microsoft Surface And Monitor

Pre-exploded PSU close-up: shown is inductor with the heatsink it shorted against.

Recently [Big Clive], everyone’s favorite purveyor of anything electronic that’s dodgy, cheap, cheerful, decidedly crispy or any combination thereof, got sent a very dead external power supply unit. Being clearly a third-party PSU with poorly written and many (likely not truthful) safety approval markings on its label, this PSU had the dubious honor of having destroyed a Microsoft Surface computer as well as the monitor that was connected at the time.

In [Clive]’s video (also embedded after the break) the black and very crispy board is examined, showing a wealth of vaporized traces and plenty of soot. What’s however most fascinating is the failure mode: instead of something obvious like e.g. the main transformer between the primary and secondary side failing, here it would seem that an inductor (see heading image) on the secondary side had its insulation rubbed off and shorted on a nearby heatsink. A heatsink that just happened to be also electrically connected on the primary (mains-level) side.

Judging by the former owner’s report and aftermath, this led to a very sudden and violent demise of the PSU, with mains power very likely making its way into the unsuspecting Surface system and connected monitor. The number of ‘very nope’ design decisions made in this PSU are astounding, and a lesson for both aspiring EEs and anyone considering getting a ‘cheap’ third-party replacement PSU.

(Thanks to [Helge] for the tip)

55 thoughts on “The Little Replacement PSU That Could: Kill A Microsoft Surface And Monitor

  1. Had a very similar thing happen to my Butterfly Labs Bitcoin miner back in the day. The supplied PSU must have been running close to it’s limit as within two weeks one of the output caps had swollen, bulged upwards and made contact with a live heatsink.

  2. Trust me. This happens a lot. I’ve been doing failure analysis for 40 years and it’s certainly not limited to low cost items. Mechanical engineers rarely see the potential failure points.

    1. I’m a Electronic Engineer that specialises in PCB layout, and I have had some experience with Mechanical CAD. I use Pulsonix for PCB CAD and Solidworks or Solid Edge for 3D Mechanical CAD.
      For several years now, since at least 2015, we’ve linked 3D STEP models of components with our library footprints and have been able to view PCB designs with enclosures within Pulsonix, with mechanical “clash” checking, and also export and import STEP with the Mechanical CAD assembly.
      We design to standards with specified requirements for creepage and clearance, and check to make sure there’s sufficient clearance between live areas and any other part of the design.

      1. Yeah, it’s a knock-off modified to be cheaper by someone who has no clue or doesn’t care.

        On the bottom of the PCB you can see a very well sized creepage area and even a PCB rout under the opto couple. Then they have put a heat sink the whole length of the board from primary side to secondary side right across the opto couple PCB rout.

        The other heat sink gives it away and it’s the one that arced over from primary to secondary. Once again it is full length passing from primary side to secondary side and it passes over the top of much of the PCB and in desperation there is even heat sink compound to the plastic case. Heat was obviously an issue.

        It obviously much larger than the original and the give away is that was intended to be primary as it’s hot with the negative of rectified AC and most importantly it has the switching transistor.

        My guess is that they have substituted a much cheaper switching transistor causing the transistor and the transformer to get much hotter and then they have tried to solve the problem using more room for heat sinks violating the original safety design parameters.

        The circuit is a secondary controlled primary regulation so it’s intended to be very efficient ie produce very little heat. They probably substituted a switching transistor that is too slow to turn off, spending more time in it’s linear region and causing itself and the transformer to heat a lot.

        So it’s not a case of dumb design or dumb designer, the original design looks quite good. It’s a case of a cheap knock-off using a cloned PCB substituted components and complete violation of the safety aspects of the original design.

        And that is *exactly* what I expect from a Made in China knock-off. I won’t buy Made in China power bricks or wall warts unless their approved, supplied by a reputable brand. I always prefer earthed devices over double insulated when it comes to SMPSU’s.

    2. This unit is not compliant in my country and I would suggest that it is not compliant for any of the countries for which it has compliance indicators (logos) on the casing.

      I have never seen an generic market PSU that is compliant with our regulations. Unfortunately people are dyeing from these things.

      It’s perplexing that they air gap the opto-coupler and then put a heat sink the full length from primary to secondary.

      1. It’s because the EE likely had nothing to do with the mechanical heat sink design. The optocoupler air gap is likely on the recommended footprint for the part, and the EE who did the schematic at least plausibly had a part in PCB routing as well. But then the mechanical design is farmed over to someone completely different.

  3. Maybe you’re too young but “Engrish” has been around for decades and refers to poorly translated English, often on items from the far east.

    I’m pretty sure /r/engrish is a thing and was definitely responsible for a lot of circular “funny” emails back in the day.

    1. I’m old enough to get it, and also understand that it’s vaguely racist term. I’d also suspect that whoever did the translation has a better command of English than most of us have of Mandarin. Come on guys, you can do better.

      1. “They did their best” isn’t a good excuse for a poor product. The people who made this PSU made a better PSU than I could, but that doesn’t excuse the poor PSU design and implementation. It’s not racist to say that people who don’t speak a language fluently aren’t fluent in a language.

  4. Reminds me when I bought a replacent power brick for a Nintendo Wii. When it came in the brick was super light and something was rattling. I opened it up and it was just some diodes, filter cap and a 2watt resistor and status led. The item that was rattling around was the filter cap. I ended up reusing the casing and power lead and stuffed in a mean well unit.

  5. A story. I purchased a second hand battery charger with battery that had a socket that said 120v in. So I made an an adapter and plugged it in and blamo opened it up and and it was clearly not mains input. Then read on the data sheet that it has an adapter for 48v dc . Why would they label the input 120v ac with three conducters. I know I should have checked it out more but it seemed so clearly marked and I stupidly only checked for a ground lead when I made the adapter luckily didn’t have the $600 dollar battery attached. Luckily it was a steal as I got it for $30 at the thrift store.

  6. Microsoft Surface chargers are pretty bad at the best of times. If it isn’t the Surface connector failing after a few months the charger just ups and dies. We have 3 Surface devices in our home, one 3 pro and two 4 pro’s. Only the Pro 3’s charger hasn’t needed replacing. For some reason we can always feel a slight tingling on the back of the chassis on the tablet when plugged in. If the the ‘figure 8’ end on the power cord is plugged in backwards, the tingling is worse. At one stage I had it plugged in to the power strip behind my laptop. I also have a few small PC’s connected to an identical board under my desk that I tend to put my feet on. These are all connected to the same GPO and well under the current rating of the outlet. I touched the back of my surface to adjust it and the tingling feeling was so much stronger to the point of it feeling like a burning or sometimes a shocking feeling. Keeping my feet off the computers under the desk or off the floor reduced the intensity of the tingles/shocks but they were still there. Must have been a strange ground loop issue with these power boards. But it was so strange that the Surface charger tingles like that. The tablet works fine still. At upwards of $150 AUD per charger you would think they could make them right the first time. But then again we are talking about Miicrosoft.

    1. I can’t comment on the Microsoft chargers but from what I’ve read, this *should* be fixable with a grounded charger.

      I’ve also had this issue on my iPad with my Apple charger/cable so it’s definitely not just you, but my charger only has the 2 pins for power. (The iPad’s metal chassis of course is great at passing along mild currents 😄).

      You can try to find a particular electronics stackexchange thread where the reason of the tingle was explained (it involved a bit of current leaking through a capacitor iirc and wasn’t a major concern most of the time).

    2. > For some reason we can always feel a slight tingling on the back of the chassis on the tablet when plugged in

      I’ve had this with quite a few devices. All of them had the same thing in common, they decouple to the GND (earth) connection with some caps. Not sure why.

      Guess you don’t have GND/earth hooked up on your sockets? As that should remove it. (or trigger a breaker, at which point you also know there is an issue)

      1. The Wall sockets are all Earthed as per Australian Standards. The power boards also have Earth sockets but something funny was going on. On the main power board I had my laptop and monitor plugged in. One day I plugged in an external HDD case that was powered by it’s own 240v to 12v power brick. When I plugged it in to the power board, as soon as I touched the USB cable to the USB port on my laptop my monitor turned off. I figured something strange was going on with these power boards so I ditched them pretty quick. Pretty sure it was making the Surface tingles worse.

    3. The tingling is perfectly normal and safe. It’s because of the noise supression caps in the power supply across the primary and secondary side. If the power supply is double insulated (figure 8 cable), you unforutnately have no good way of earthing the device and getting rid of the annoying, but harmless tingle. You could pierce the DC-wire coming out from the power supply and wrap a ground wire and connect that to a grounded point. That would fix it.

      1. “Tingle” is a well known issue with power supply designers. Without having a safety ground, there will always be some leakage through the main switching transformer. There Are specs to minimize it.

        Regarding the failed 3rd party Surface adapter, sounds like there was a failure in required HV gap specs. With proper agency compliance inspection and certification, that never should have passed.

      2. When the cassis of the Surface is painful to touch for more than a few seconds the tingling is certainly not normal. Usually if it is plugged directly into the wall or a different power board it is fine. Unfortunately the charger and cable is double insulated. Funny how no manufacturer tells you that there is a correct way to plug those figure 8 leads in.

        1. This is a serious safety issue that needs to be addressed immediately.

          Neutral is connected to earth with an earth wire from neutral in the power box connected to a copper stake into the ground. It’s sounds like this has disconnected. It’s a common and dangerous fault that is due to electrolysis.

          1. Just checked the Earth rod and it looks fine. No green copper. The House is only 4 years old. I’m wondering now if it’s a ground loop issue between the two power boards.

          2. @[Jehu]

            “looks fine” isn’t a diagnostic conclusion

            You can’t get an earth loop problem from a power board. You can only get it from an appliance plugged into a power board if there is something wrong with the power board and or the appliance. Even that shouldn’t cause a shock sensation unless there is an issue with the household earth.

            Swap around power boards as a simple way to get a better idea. If the problem goes away then cut the plug off the power board, bent the pins on the plug so it can no longer be plugged in and throw it out.

            Otherwise start testing with a multimeter (if your qualified) of call an electrician.

            If your qualified –

            Test the voltage between neutral and earth on the power board is should be less than a volt or two perhaps higher if you have a fridge or air conditioner plugged in there.

            Do you have RCD’s in the power box?

      3. Yeah…NO! If you can feel a tingling, there’s a problem. Use an AC milliammeter between the chassis and the ground pin on an electrical outlet. A GFI outlet will trip at nominal 5mA.

        IEC 61010-1 section 6.3.1 specifies a maximum 0.5mA RMS in normal operation.

        1. The outlet is a standard HPM Vivo double GPO. The circuit breaker has an RCD but no GFI. Looks like I’m going to be doing some trouble shooting tomorrow. I’ll check with some of my other DMMs tomorrow.

        2. In Australia we use Earth Imbalance Breakers (no connection to earth) that are generically referred to as Resettable Circuit Devices (RCD’s) and the specified leakage (imbalance) limit is 15 mA for domestic and 5 mA for medical.

      1. Yeesh. Makes you wonder what it’s doing to all our 5v phone chargers.

        It’s hard enough to find any type of charger that accepts a 3-prong cord. Most are all figure-8 leads. Laptop chargers being the exception although every Surface charger I have seen is figure-8. Not even high power USB-C chargers/PSUs are Earthed

      2. In Australia a device has to conform to one of two standards.

        1) An earthed device, any user contactable conductive elements (surfaces, screws, knobs etc) must be earthed right back to the earth pin on the outlet plug.

        2) A double insulated device, there must be no user contactable conductive surfaces that do not have at least two levels of insulation like (regulation conformal) air gapping, a transformer with relevant isolation specifications. So for example you can have a completely enclosed device encapsulated in a plastic enclosure and have a metal part on the outside (perhaps a brand logo) as long as there is no way the metal on the outside can come in contact with anything on the inside.

        A double insulated device has a symbol of a rectangle within a rectangle, near the specifications.

        Then things become more complex when a device runs on a power brick or wall wart.

        If the device itself is double insulated then you can use a double insulated brick PSU (two pin) or a 3 pin PSU.

        If the device is not double insulated then you must use a 3 pin PSU.

        We have far to many non-compliment wall warts or power bricks coming into this country now and people are dying from these.

        I wont use anything with a two pin (figure 8 cord IEC C1 C7) cord unless the cord plugs directly into the device, it’s a reputable brand and it has an internal transformer to do the voltage conversion.

        At least IEC C17 is polarised and likely safer (most situations).

        Any wall warts or power bricks in my house must be three pin IEC C5 or C13.

        The exceptions are 5V USB chargers which I keep away from earthed appliances or where there is plumbing like the sink.

        Most of the deaths (associated to non-compliance generally imported from China goods) are when a non-compliant double insulated device is used along side and earthed device and a person makes contact with earth on an earthed device and fault induced voltage on the double insulated device. RCD’s can protect from this situation but RCD regulations vary by state and in some cases are not required.

  7. Nothing wrong there, just treat it as a warning sign. The designer of this product could have stumped up the cash to get a proper translation made. Instead they passed the job on to a mate who clearly wasn’t competent. Even with the lack of hindsight we’ve got from the failure, how much confidence do you have that they didn’t hire their circuit designer, board layout person, component buyer, QC people etc. using the same criteria? Think of it as the poor man’s version of the band rider clause for a bowl of green M&Ms.

    1. In the 90’s many of the cutting edge NCR cash registers were designed and built in Japan. The manuals for us Field Engineers we’re in a borderline bad translation we called “Japlish” (I mean no offense). Some features of the cash register were set by on board DIP switches. To enable a certain feature the manuals instructed us to “insert switch to on”. It got worse from there.

  8. Problems arise when you want to connect that tablet-laptop to an amplifier for a good audio connection, and bigger surprises when plugging in the male amp connection last. BUZZZZZ! pop.

    I try to have 3 prong power supplies on all my live gear and know which don’t have to be left connected in order in tear-down-setup. FLOATING label on any such power supplies. They are safety rated the caps that do this, they used to be wax-paper and were called death caps. Now the global safety ratings label on that cap also says Made In China. ???

  9. “The number of ‘very nope’ design decisions made in this PSU are astounding”

    If I recall the video correctly, there were just two main(s) concerns: the heatsink being live and the choke being too close to it.
    Bigclive remarked that this could have been prevented by a little isolation on the choke.

    1. This article is an object lesson that more often than not you get what pay for when you purchase a no-name electrical device from your favorite auction web site. While a name brand, Microsoft in this case, replacement part is likely unfairly over-priced, a generic replacement which costs perhaps one quarter is probably leaving out important safety engineering and/or important safety components. Of course price alone is not a reliable indicator of quality or lack thereof.

      To an average consumer, a dangerous cheap part generally appears the same as a reasonable quality part, If one is lucky, obvious misspellings on labels might give an indication something is amiss with bad part. Unfortunately, manufacturers are getting better at making exact copies of original parts which contain junk on the inside. I have seen fake AirPods Pro which are indistinguishable from originals in retail packaging and outside product appearance. Only upon disassembly can it be seen the internal components are $2 Bluetooth ear buds and steel weights are used to simulate the mass of missing components in the ear buds and charger case. The fake AirPods Pro lack noise cancellation and have poor sound quality. Unfortunately the purchaser’s money is already gone by the time the scam is detected.

      The twofold problem is that both countries producing fakes for not better policing the manufacture and sale of fakes, and the consumer countries for not doing a better job of preventing importation. Policing on the import side is admittedly difficult because it is close to an impossible job to provide enough expert personnel to spot fakes of every conceivable product which might be imported.

  10. @[RÖB]

    I Couldn’t do much more than a visible inspection as it was 1:30am and chucking it down raining. about 60mm of rain at that point. Otherwise the joint looked secure to the Earth rod.

    Both power boards have been replaced with new ones but the problem remains. Old ones were Bosston Audio Visual 8 outlet power boards replaced with a HPM 8 outlet board on top or my desk for the laptop and a Crest Tool Guardian 5 outlet with lights for under the desk which supplies two lamps and two desktop PCs, both turned off.

    I did some probing between the chassis of the Surface and other places. I used my Fluke 112 True RMS meter and a Digitech QM1323. With both the meters, on the current setting with the probes in the correct sockets and the voltage (Red) probe to the Surface, the Surface would sit between 5-9v AC with the COM lead of the DMMs not connected to anything. When I touched the COM (Black) lead to the chassis of one of the computers it measured ~88V AC.

    Interestingly, I had a bare PC case in my room, with no power supply and not connected to anything and the COM probe to that read between 25 and 48V AC.

    I then tested my Surface on a different circuit. COM to the Kitchen sink measure 101V AC. Dad’s surface and his power supply measured 104V AC between the Surface and his PC chassis.

    As the house is only 4 years old, all power circuits have Residual Current Devices fitted.

    So even without the power boards I’m still getting this 80-100V between the Surface and an Earthed object.

      1. With the shortcuts the tradies made when building this house, nothing surprises me anymore.

        This might explain my HDD dock turning my monitor off when I plug it into the USB on my laptop. The dock only has two prongs and no earth. Figure-8 lead straight into the dock.

        I’m starting to look sideways at any double insulated, unearthed plug packs I have, even when they are from a reputable company.

  11. Stuff like this happens at OEM levels as well.
    A certain toy using a flourescent light source was powered by 4 C cells.
    All worked fine and passed inspection.
    Two weeks went by before we started getting returns of which a few were of the smoking variety.
    One had caught fire and was crispy.
    Tested the smokers. No issue. Hmmm.
    I did a full teardown and circuit trace.
    Something just didn’t look right.
    I had a pocket uv lamp and did a comparison.
    All components were exactly the same except for one small detail.
    The output was floating.
    Aha I exclaimed just a little to loudly for the QA office.
    I searched the battery drawer for a set of low voltage cells. Yip, I was right. As long as there is enough power to get the lamp to light power would be drawn. As the voltage dropped the current rose and components would loose their vital smoke.
    Product management wasn’t happy with the recall but the CPA had gotten wind, so no sweeping under the table this time.

  12. In Australia we have 240Volt mains so the same situation that in America will cause “quite a shock”, in Australia will cause fatality buy electrocution.

    Australia is also the “dumping ground” for old technology especially from the US. Most American consumers want something that is “the latest” and the price consumers are willing to pay for for something that is no longer “the latest” drops very rapidly so they dump these products in Australia because dropping the price further in the US creates an expectation for the next “the latest” to be cheaper. However Australian consumers compare features and functionality with little regard for something being “the latest”. So this is one path of problems here because ex US junk doesn’t have the right power brick (wall wart) for Australia use.

    The other problem which source which is unfortunately the same with ex US products is usually China.

    For Ex Us products, the manufacturers pair the goods with a made in china power brick (wall wart) and they just look for the compliance tick that indicates compliance with Australia regulation. Of course most of these have never applied for or attained certification as save for Australia, China just copies the approval emblem. The problem here is that you have otherwise reputable companies supplying reasonable quality good pared with a potentially fatal power brick (wall wart).

    The other problem is direct imports from China and that far exceeds the power brick (wall wart) situation and we have products that plug directly into the live mains outlet (without a wall wart) that is downright dangerous.

    Many Made in China products are primarily designed for the US (110Volts) and then modified to be sold in Australia.

    Fro example, something that heats, for the US will have two 110Volt heating elements in parallel and for Australia will have the same two 110Volts elements in series. This presents a number of problems. The first of which is that it’s now suited to 220Volts and not 240Volts so the power difference can be significant and cause failures.

    The next problem is that PCB creepage (clearance) is for 110Volts and two small for 240Volts. I have fires from this.

    So here in Oz, the wiser people scrutinize and mains devices very carefully for clue of non-compliance. There have been fatalities.

    Having said that, I have seen some tear-downs of products on US markets on Youtube that look positively terrifying.

    We have a good compliance rate in this country but there are exceptions and failures in the process. Goods detected to be faulty are withdrawn from the market and recalled from customers. In America, it looks like once it gets into the country there is no secondary process to remove dangerous items.

    The worst I saw was power cord with a standard Australian 2 pin outlet plug (active, neutral, but no earth) on one end and a IEC C13 three pin on the other that came with a laptop power supply.

  13. Wow, not only were a lot of original comments removed, but also my comment on the comment system showing the total number of comments, including the hidden ones. So instead of thanking me for pointing out the bug, you’ve deleted that as well. Good job HaD!

Leave a Reply

Please be kind and respectful to help make the comments section excellent. (Comment Policy)

This site uses Akismet to reduce spam. Learn how your comment data is processed.