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Xiaomi 4K Laser UST Projector Repair (white vertical lines)

Some of the owners of Xiaomi 4K mijia laser projector (or Wemax one, Fengmi, e.t.c) facing some problems in the operation of their projector that actually make the projection…nightmare.


What are these problems?

-The projector has slow boot, it can take 10 minutes from the moment we press the on button on the remote control

-After some time of viewing or immediately after opening in half the image, white vertical lines are observed

-After some time of operation, white dots are observed in the image

-Random restarts


For all these problems the cause is one and only defective part..

An accessory to the optical engine that has a manufacturing error, let’s go to see in detail the problem and the solution starting with some basic instructions disassembly the projector.

The white lines look like this…



To remove the projector housing, we must first untie and remove the Ι/Ο card. Remove these two plastic pieces, unscrew the 2 screws we find underneath and remove the card



After unscrewing the screws at the bottom of the projector, we can remove the housing. As soon as we remove it, we’ll be in front of this picture…



Unscrew and remove the metal protection over the mainboard and begin to disconnect it from the various plugs that are buttoned to it with the first large cable that connects the optical engine to the mainboard. Three screws are the ones we need to unscrew and then carefully disconnect the cable.



Attention is needed to disconnect a few more flat cables that we will find connected on the mainboard



It should be removed and this fan, which is not screwed anywhere, we just grab it and remove it..



After we have removed the mainboard then we are ready to remove the optical unit. 4-5 screws are the ones that support it in the chassis, once we remove them we can remove it..



After we remove the optical unit, our projector will look like this.



The problem is on the optical engine, so will work on it…



Next step is to unscrew the DMD Chip’s cooler…



Then carefully remove the two screws from the metal surface and remove the flat cable



This is the cable that makes it possible the communication between mainboard and DMD chip…



Here we can see the contact points



And we come to the source of evil, which is no other than this piece of metal that actually presses the flat cable to make proper contact with the DMD chip



But what’s going on, and how does this metal piece cause such a big problem in the projector?

This metal piece is a cast metal which shows little resistance to the high temperature conditions prevailing in the optical machine resulting in bending.

Yes well heard, bends and no longer presses evenly the flat cable on the DMD chip

If you look closely you will see the “curb” that has been created…



And here with graphics a little more understandable the alteration that has been suffered




The solution

I tried to solve it in many ways. At first I just bent this metal again and restored it to its original form. I tried it for a few hours on the projector but found that it started to lose its flat surface again and started to inflect again!

This time i realized that no solution can be found with the existing part. Even if I bought it new as a spare part, it would probably give the same malfunction in a few X hours.

So I started thinking about building a new one.

As a first step I made a copy in hand of brass (easily worked by hand) and tried it. In fact, I changed his shape and gave him larger dimensions where it took me to do it, so he could create a larger contact surface!



100% success!at the begining at least…

But I didn’t stay there. As a restless spirit I wanted to get to the end!

If the plate does not have exactly the right details and thickness on specific points it can cause other problems (DMD chip overheating, big pressure on the LGA250 DMD plastic socket, e.t.c)

So I proceeded to design the accessory and manufacture it in Laser CNC with experiments on metals and their strength (a new world opened up in front of my eyes and I dived in!).

So somehow I created a lot o f versions to try them but the results was not what i want and expect , some of them starting to inflect again like the original, other didn’t offer the perfect contact for the DMD i had in my mind…



So i finally after almost three months of testing and research i succeed to make the final version on a CNC laser with perfect accuracy on the thickness and the details. Also this plate is a mixture of metals based on stainless steel SS316 which with the addition of 2 more elements acquires incredible resistance to temperatures and pressures (we are talking about crazy research, running in machining and MANY tests to find this metal). Maybe I’ve overreacted… but it was worth it!


After a lot of tries this is the final version that i have made a lot of tests and works just perfectly …



The greatest satisfaction for a technician is when his efforts to find a solution to a problem come to fruition. And in the case of Xiaomi 4k laser projector, the satisfaction came, with VERY toil, but came.



The repair video


In case you experiencing this problems in your projector and you want to solve it permanently, you have to replace this part , you can manufacture it (but be sure about the CNC laser accuracy you going to use otherwise you will cause bigger problems on your projector!) or contact me if you want to make and send you a copy of this final version of the plate. You will place it in your projector and you will solve this “factory” problem once and for all. Of course if you don’t feel capable το replace the part by yourself you can always send me your projector to repair it for you!No problem.

(My advise is that until you replace that plate DO NOT operate the projector, there is a possibility to damage the DMD chip with this poor contact)


You can also read my full review of the Xiaomi 4K laser projector here https://www.projectorjunkies.com/xiaomi-4k-ust-projector-review/


God bless you all

Nikos Tsolas


  1. Jacky says:

    Amazing, my xiaomi is experiencing the same problem as yours, and mine one with the black lines as well..
    Can I have the contact of the CNC store, please?
    I would like to fix mine one, otherwise I will have to buy a new projector..


  2. Ary says:

    Mine is taking a few minutes before turning on. I hope that this new piece will correct this issue. Thank you for your work. I am interest in this new piece of metal. How can I please get it ?
    Best regards

    • Jacky says:

      Hello Ary

      Have you found the right metal for the part?
      I just disassembled the projector and getting the measurements, and I will build a CAD based on it. But still looking for the right metal to use, I saw Nikos is using ss316 but I wonder if it is suitable for transferring the heat as well.


      • Bob says:

        Hi Jacky,

        Did you manage to build the CAD file?


        • Jacky says:

          Yes, I drew one, and looking for a CNC machining company.

          • Bob says:

            Would you mind sharing the file? I found a company here during my holiday but I don’t have the projector with me to copy the piece. Happy to share the info about their suggestions regarding the material after the visit.

          • Jacky says:

            I am happy to share it, but I am not sure if the piece fit to the projector, and I do not want others using the wrong measurement. I found one company, and they can cut and ship me the piece in 20 days. I will definitely let you know further.

          • Tsolas Nikos says:

            From my experience is very difficult to copy this plate. In the start i said, ok,it is just metal, not big deal, right?no no no, it is a big deal. If you don’t make all the details exactly as they are, it does not fit and the DMD cooler can not fit as well. I try three different CNC lasers and i have make more than 10 plates in order to finally make the one.
            The CNC lasers can not stop the production and spend time to make one or two pieces with so much details, they drop you.To just cut the metal is very cheap and easy, but this is not the point (something like 2-3 euro per piece), to design and make the details is that CNC does not accept to do it, and if someone accept, the cost goes high at 80-100 euro per piece (the better price i take was 80 euro each for 50 pieces).
            The other problem is the metal, i try 3-4 different well known metals that the CNC work with mostly, and ALL inflect after 30-40 hours of use only (not at the point to start the problems,not so much like the factory one, but i knew that this was not the permanently solution i was looking for), even the strongest one.
            Of course when i return every time to the CNC store to say about the metal is not so strong as they said to me, they always told me that they are not responsible for the use i will do on this metal piece and i paid again for the new one.
            If you have a thin metal plate under pressure in the heat it will inflect at the end, even least, i didn’t know that, i have learn now.
            If it is inflect even a half millimetre (you can not see it by naked eye, every time i put it out from the projector and go to the CNC store to measure it) it will cause problems like delay start at the beginning and bigger issues at the future.
            For me to finally find the CNC laser with the most accuracy on the details and the patience το deal with, the right metal with the correct aids on the spots i have pointed out, to find out that you have to make the plate a little bigger than the original because the final procedure (that i am doing to a different machine shop that is specialized on that), the shine (you can not push the flat cable with a non absolutely shine metal, you are going to make a damage), does effect on the final fat of the plate (oh yeah) and you must have already calculated it (if not,the plate will not fit correctly, trust me, i HAVE PAID this), all this cost me more than 1000 euro and over 3 months of time and tests.
            Right know all these details is on my CNC laser guy (and the special mix SS136 metal that i buy it from a specialized metal store here in Greece, this week i am going to buy more and i will inform you guys what exactly is the mix) and the shine specialized store and i am just call and ask them to make me a copy. At the moment i am waiting 10 more copys next week because i have already 5-6 requests from people all over the world ask me to send them one.
            I am very curious what will be your story guys if you try to make a copy of this plate to your local CNC laser store, and if you finally succeed to do it how this plate will behave throw time and heat on your projector. If you want, please share it here, it will be very interesting…

          • Jacky says:

            Thank you for sharing the process with us, Nikos, it is very interesting and challenging. For finish of the metal, I never thought about it has to be shine finish, no wonder the original one has the plastic sticking on the back. Yes, I believe it is no easy to copy the exact same one, even I drew a CAD for the piece, I am still not sure about measurement.
            Please let me know how can I order one from you.
            Many Thanks

          • Tsolas Nikos says:

            i always share my repairing procedures on my blog Jacky. If you want to send you a copy of the plate just email me your shipping details.

  3. Ary says:

    Hi Jacky,
    Woaw. Sorry. But I am not as qualified as you 😉
    I didn’t disassemble it yet. And I am expecting Nikos to help me find and buy this piece of metal. Then the Next stage will be to mount it.
    But really, I am interested if you manage to do it by yourself. Happy to share your experience

  4. Vad says:

    Hi guys,
    The same here.
    Once I left it running overnight, normally it goes to sleep but that time it didn’t.
    Next day boot time degraded, then it started degrading more. then some artefacts started appearing. Boot time went up to 10 min or more (not the actual boot time but the time it needed to start throwing the picture).

    I found there is another issue with this projector. (another data cable). That kind of worked- boot time reverted to normal but more white dots appeared over time.
    So I hope Nikos would be able to help here.

    Please see workaround for another design flaw posted by user ‘huntereye’
    hi, I believe issues such as white pixels, distorted color and slow starting were all caused by the same issue, which was a design flaw of the data ribbons near the center of the projector. I ran into these problems 6 months after I bought the projector. I managed to fixed the Xiaomi 4k projector problem recently by opening the cover and grind the plastic ridges off at the back of the cover (see pictures attached), the ridges put too much pressure at the grey data ribbon near the center of the projector hence causing the image problem.

    it’s worth mentioning IO card removal trick – you should press the center as it is thinner and you would be able to pry this piece easier.


    • Tsolas Nikos says:

      The design of the ribbon cable is just fine. The cause is this metal that holds the ribbon cable (read my article). This is the reason, not the ribbon cable.

      • Jacky says:

        Hello Tsolas

        I was able to flatten the metal, it is ok for now.
        Could you share the CNC store and the material you used to replace it?

        Many Thanks for sharing

        • Tsolas Nikos says:

          That’nice.The problem is that in few hours (100-200) the metal will inflect again (from the first 2-3 hours i measured a small bend again already), that’s why i try to find another solution with another metal part. The CNC laser is in Greece, the metal part after trying different materials is a SS316 with other two elements inside (i don’t know them, i can ask the CNC store, they suggest that metal). This is the only metal that we measured no bend at all after some hours of heat.

          • Jacky says:

            Thank you. It will be great if you can let me know the name or code of the metal. It is great that you are a restless spirit so my projector can be fixed!

            Do you know how different is it from the ss316?
            I know ss316 and ss304 are easy to access in US.

          • Tsolas Nikos says:

            let me ask for this and i will come back to you!

          • Lati khan says:

            Hello I am facing the same problem in my projector so CAN I please give me the metal part?? I will be very grateful to u

          • Even says:

            Hi. Do you have the measure of the part you have made?
            Hight, width, thickness, mm for screws etc.

  5. Jhon says:

    Do 100% projectors have this problem? If not, what is the difference between them? What is the difference between them?

  6. Roy says:

    Dear Nikos,
    I’m facing the same problems with my 4K projector after 9 months after buying.
    Do I need special tools for demounting all the parts? what will you charge if I want to buy the replacement part?
    Looking forward to your reply.

  7. Bart says:

    How much this part with shipping to Poland ?
    Do you have STL file or other 3d model..?
    Best regards

  8. Vic says:

    Hi Nikos!!

    I have exactly the same problem. I would like to buy the metal part from you! I can we proceed?

  9. Mike says:

    Hi Nikos! I have the same problem with my Xiaomi 4k cinema. I disassembled projector, find out curved piece of metal and made my own. But problems didn’t disappear. Then I disassembled it again and looked at the pinned plastic between chip and cable. Some pins were bent. I corrected them in the right place, but the second approach also had no effect. Now I plan to take out plastic and correct all pins, cause I have no other ideas. I’ll post here the results and can send you some photos of the process to your e-mail if you share it to me.

    Regards, Mike.

    • Tsolas Nikos says:

      Mike can you send me photo of the metal plate you have made?Μy email is on contact page. I ask you because the first 3-4 plates i made didn’t work.It took me a lot of time to find the CNC laser that was able to make the exactly copy of the original. Also have you measure the plate again after the polishing process?Because it loose a lot of micrometers on the procedure and this could cause problem on the DMD contact. If the dimensions on the plate details are not exactly precise then even if you tight the screws and everything seems ok, the pressure on the ribbon cable is not the one that it should and the contact on the DMD is not the ideal, so the problem remain (keep in mind that on this optical unit everything expand and shrink with the heat), also if the pressure is bigger you can destroy the socket and damage the pins (this is i suppose happen to you).Anyway you can search and find this socket and buy it if you have destroy it, it is a LGA250 dmd socket (google it). Also the material of the plate must not affected by the heat. If you have a micrometer try to heat the plate you made well and take measurements to see the metal behavior.As i have already say it seem too easy to make a copy of the plate and replace the original, but is not!I have learn this on the hard way…

      • Mike says:

        Thanks a lot for the quick response! As promised, posting here news from my further investigation:
        1. First of all I restored the original plate and put it back in place. This allowed me to temporarily exclude the factors that you wrote about. The result is that the vertical lines have not disappeared.
        2. Then I carefully examined the nature of the vertical lines and found that they carry color. Moreover, they inherit color from each previous line to the left. This means that the contacts on DMD are not broken and the plate in my case works as designed.
        3. Then I went to the engineering menu in projector and ran a series of tests. The most spectacular are black lines on a white screen.
        4. Also I measured the tempreture of DMD chip in a working state – it was around 40 C – not so hot as I thought before.

        So: the symptoms are similar only at first glance: instead of white lines, there is a mixing on the X axis. It seems that the problem is with the video card.

        Not having the proper tools, I took projector to the service center. I look forward to the results tomorrow.

        Photos I’ll send to info@projectorjunkies.com in a few hours.

        • Tsolas Nikos says:

          Mike i have seen your pictures.Oh man,what have you done there??First of all the plate you made does not have the details that must have in order for the cooler to contact properly on the chip, is not only about thickness! Second you are not using the original screws with the stop they have on plate (probably you couldn’t make such a small screw thread on the plate and you make them bigger?). What can i say, good luck my friend but for me, you have cause all these problems, probably you have damage the chip too (you dont even have a thermal pad to the back of the chip!). May i ask why you make all these modifications and repairs to that poor projector??The only problem you had on the beginning was the inflect plate i describe to my repair, nothing else.

          • Mike says:

            Let me explain some points:

            1. Yes, indeed, the plate I made is different from the original. Is it problem? Yes and no. As I said above, with this plate it works like a restored original. The result is the same: nothing changes. You may doubt this, but it is a fact. I’ll be happy to be wrong about that. But now I do not use it any more. An ok, the screws for that plate were mine, as long as the original ones. So the cooling pressure was the same.

            3. Thermal pad is present of cause – I replace it with a thermoplastic with better thermal conductivity. This step is required because you cannot reuse an old one.

            Note again: I have restored the original plate and install it with the original screws. The termal pad exists, the contact is just as good, I measured the temperature of the chip, it was about 40 C. And result is the same, as you can see on photos.

            Now I’m waiting for the results of the service. I’ll post them here.

          • Tsolas Nikos says:

            Mike what can i say?yes, it is problem if you don’t make the details on the two screws on the plate. The screws stay out and the cooler can not make good contact to the chip, you can burn the chip even with few minutes of not properly cooling, then you will wonder what happen. However, good luck with your repair, keep us infromed.

  10. Even says:

    Hi. Do you have the measure of the part you have made?
    Hight, width, thickness, mm for screws etc.

  11. Sambeet Mohapatra says:

    Hi Nikos,
    I have sent you an email requesting the quote for the metal piece. Can you please reply ?

  12. Roberto says:

    Hi Nikos and all the brilliant minds in this thread. Nikos, my projector case is in rough conditions after me trying to take it apart over the last few months and not figuring out about the IO card. None of the forums mention that, I appreciate you posting clear pictures. Than you.

    That said, it’s functional, after it heats up I’m able to wiggle the case to the point there are no lines but I’d like to fix it before I’m tempted to bu another one. I’d love to send it and have you repair it for me, would that be possible? (Happy to pay of course)

    • Tsolas Nikos says:

      thank you Roberto, sure you can send it to repair it for you, you are living in Europe i suppose. Send me an email to arrange that.

  13. Miguel ñ says:

    Hi. Thanks so much for sharing your knowledge. I tried to contact with you with not luck. I’m interested in the famous piece. Please contact me by mail if possible.

  14. huntereye says:

    hi I can acknowledge the white pixel problem was not from the ribbon cable, I have tried loosen the projector case by unscrewing all the screws (to relief some pressure), it improves the slow boot problem a little bit but the problem is still there. So i guess ultimately the metal plate that is holding the DLP chip needs to be replaced.

    Every time when my projector starts up, it will give the white pixel dots problem, and if I wait for a min or two the projector image will come back to normal, I suspect it was because the metal plate was heated up and expands, then the DLP chip can have proper contact with the ribbon cable.

    • Tsolas Nikos says:

      yes Kevin, your porblem is this plate. If you want my advice DO NOT play the projector until you replace that plate if you dont want to damage the DMD chip.

  15. Paal says:

    After i straighten the bend metal part, my picture is gone very dark. 🙁

    • Tsolas Nikos says:

      Paal how exactly you straighten the plate?By your eye?It have to be perfectly straight. If your picture is dark that can be a wrong seat of the DMD.

      • Paal says:

        I have now made a exact copy of your plate of the steel that you use. The projector works perfect, the stripes are gone and the startup time is as new.
        All thanks and credits to Nikos for sharing all his work around this.
        Use Nikos if you are affraid for doing this yourself. Or if you buy his plate, be carefull with the contactplate between the dlp and the cable where the problem is.
        Thanks Nikos, Great work.

        • Tsolas Nikos says:

          my pleasure Paal!i am happy that you finally fix your projector!enjoy!

          • Michael says:

            Hello Nikos,

            I would like to have 2 of your Master Pieces 😀
            Where can i find your email to get Futter information ? Or could you please contact me ?

  16. Mark says:

    Is there any model type that does not have these issues? Or do all models have this issue?

  17. Michael Huynh says:

    I am interested in the plate. How do I go on about receiving one Nikos?! Mine have started flickering and wouldn’t turn on until you attempt to turn it on like 5-10 times.

  18. varra says:

    Tsolas Nikos
    Are you selling that plate?

  19. Stephan Eisermann says:

    Hi guys,

    did sent my projector from Germany to Greece and got i back today – bootuptime now is as it was when its was brand-new from the factory. Nikos is a super nice guy, communication went really well!

  20. Pierre says:

    Hello, I am interested in that Projektor too. The 4k1s i would take.

    Is that issued with all of that Prjojectors?

    @Niko: If I will get mine, how can i test If that issue is with this Projector? And If i have the issue can i send i to greece too?

    • Tsolas Nikos says:

      When that metal starting to inflect you going to have slow boot and some times white vertical stripes on the picture.On that point you have to replace this plate. Yes, you can send it to me when the time comes to repair it for you.

  21. Marcin says:

    Hello Tsolas.
    I have the same problem in my projector. Maybe you have more of these parts? I would gladly buy 1 piece from you.
    What would be the cost with shipping to Poland?

  22. Roel says:

    Hi Nikos, I like to thank you for this excellent solution. I had already declared my Xiaomi projector almost dead before I came across this web page. Rather painful considering it price back then and knowing I only owned it for just over 1 year. Anyway, the shipment of your metal plate went incredibly fast. Your prompt response to inquiries and friendly communication ensure that I recommend your help to anyone with this projector and its design flaw.
    My projector works again if its brand new. Very happy with it and that I came across the projector-genius of the internet;-)

  23. Aziz Adli says:

    Hi Nikos, Im from Malaysia, im really interested in buying this metal plate. can i get a quote, i really want my projector working as long a possible.

  24. Christian Manzini says:

    Hi Nikos,

    just sent you an email regarding the metal plate.

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