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Hi Colleges

I recently bought a Sunhokey machine 2015 version. I assemble everything according to the instructions included in the DVD, calibrate everything, and print a lot of the projects for the machine that I found on thingiverse using the SD card.

When I try to use CURA an connect the printer via USB, my USB cable burst in FLAMES!!!!!!
also this short circuit damage the USB port in my computer...

I did some measurements with my voltmeter and found that the power supply ground was at 12V. Everything was correctly connected!.
I found that the M4 screws fixing the power supply to the acrylic wall were shorting the 12V rail to the PSU physical ground. The right-bottom one is directly behind of the 12V rail of the PSU, and if you use the M4 screws recommended in the instruction DVD, you will go trough the plastic film and short the ground of the PSU to the 12V rail.

Please guys be careful! Do not over-tighten this screws, use shims to avoid going through the film inside the PSU, or simply do not put the Bottom-right screw. Your USB cable and port are in high risk, I think this is even a fire hazard, I hope you take it into account.


Grazie per l'avvertimento

Thanks for the warning, i will begin assembly tomorrow.

Be very careful guys ..... I got a spark then a mild electrical shock, while trying to adjust an M5 bolt securing my Y carriage and hotbed to the aluminium frame of my HICTOP 3DP11...... the similarity is the power supply is mounted to the aluminium frame by four M3 bolts onto a metal back plate as described in this forum topic.
I am thankful I found this discussion online, thank you for posting up .
This potentially fatal manufacturing ERROR needs addressing and making public !!!!

It is true that you cannot over rely on electronic machines as they can fail at any time therefore you need to be more careful while using them. Most of the short circuit happens when there are some technical issues or faults in the connection line but water is another factor that can often lead to some unexpected event. That is the reason it is being advised to take assistance of New York City Fire Damage Restoration Company during floods rather than putting your own life at risk.

Crap. I better check this when I get home. Haven't had any any electronic dramas yet (Touch wood).
Thanks for the heads up and commiserations to those who have had problems like that so far. I only had relative short time so this could still come and haunt me.

I too have had the heatbed get very hot and burn due to bad solder joints and had the insulation layer up in smoke, just terrible quality electronics. I emailed sunhokey, in their response they said 'I must of miss used the product' and gave me a link to BUY another one, as much to say I didn't and have replaced the bed with a more reliable supplier...

Another WARNING: the white fluffy material on the buttom of the heated bed can burn.. I smelled something wierd after printing for weaks, even saw a little smoke. Killed the print and it turned out i had t short circuit or bad connection on the heated bed which put the fluffy stuff on fire..

yep i moved on not too long ago after the bed flat out Burnt out the smells pretty rough

but yeah i can see why people move to MK2B beds and glass the warp issues that can occur in abs are non almost non existent 107c in around 4-8 min consistent and even

Found this website 1 hour too late. Burned out a computer USB port and overheated a USB cable. Found the bag with a folded message (visible with M4x8...). The -V port was 12V above house ground. With the shorter screws, both the -V and +V ports are now within 0.4V of earth ground. Does this seem reasonable?

just change the bed to another.. there no need to do repair like this, i bet any other bed would heat faster than the original sunhokey bed.

Replace the 4 original screws M4x12 with M4x8!!

Yep, this is a real danger - I noticed the thing while screwing the screws, soI used the shortest ones possible. Happy to avoid this. Sorry for you, man, but thanks for sharing this!

Yes i have notice that the screw showed in dvd is too long, but there was a little bag of screw with "power supply" writed on it. so I have use this at first. Later i have printed a thing, look at my profile, to separate the power from accrylique and so used long screw.

That is never a good thing. I was not happy with the poor air flow to the PS. Being that, I put 12mm standoffs between the PS and the chassis, mounted with nylon screws. Never liked inserting metal screws into enclosed power units. Regards

hey man, im sorry to hear that :( i realized there was a bag with smaller screws inside my kit with a warning to use those instead of the ones in the video for the PSU but they wouldnt fit so i used the ones in the video anyways and everything went ok. perhaps the ship two kinds of PSU's?

ill take it into consideration and put a coule of washers in between the psu and the acrylic anyways

For the first weeks i used it with PC too. The longer screws did make their way through the insulation over months and with the vibration a printer always has. Please be carefull!

Mates you made my day... i used my printer for about 3 months now stand alone and considered it absolutely safe. Since it is my third one i wanted to sell it and show the friend how to use it. Hooked up on USB... boom. The inductor blew up initially. Also it killed 3 of the steppers. I thought the board might be faulty so i hooked up my well loved MKS Sbase 32 bit... you can imagine what happened then. If i might meet one of sunhokey i would slap him to death. I fixed the insulation with 3 sheets of kapton and applied shorter screws. Also i shorted the blown up component. I will observe the printer for a month now, before i let it print unspectated! This issue is for sure the worst thing i have ever seen.

Hi, I think i have the same problem with the power supply.
When I plug in the power supply, nothing happens.
Is this the consequence of a shortening inside the PSU?
When i measure the voltage on the power output, it is zero, and also the green LED does not lighten up.
If it is the PSU, does anybody know a solution? I want to buy a new one, but how can I be sure that the board is not broken?


You can, at least, test the board logic parts - disconnect the powerr, switch the jumper in the middle of the board and cvonnect to pc. It is basically an arduino, so you should see serial communication ging on (lots of "wait" messages). Of course, this weill not tell you anything about steppers or stepper drivers. Btw, there is alslo a fuse in the PSU - check that one, too.

I have same problem with the power supply, I missed noticed an extra little bag of M48 screws with a thin strip of paper
"Attention:fasten the power supply in the acrylic part with M4
8 screw" because I focus on video tutorial (put m4x12mm screw).
But not damage main board only broken power supply. If i put cable to power line, MCB trip. previously I used to running test motor is running well, but after I unplug cable from power line and plug again trouble come. I think was not strong power in my home but it was not. After i check power supply, unplug cable output (12Vdc) trouble persists, the power supply broken and try to repair. after I open the casing of the power supply, yes 4 screw behind the hole is rail of the power supply and separate with plastic film. lucky plastic film not broken and short the screw to rail PSU. but screw make the remaining pieces of "foot component" (capasitor) flexed and short circuit, make (+) and (-) DC 220V short circuit. I try replace two component 13009 (npn power switching transistor) and it's works. hope there is no problem anymore. but there is little disturb me about the installation of 5 pcs heat sink in main board, worry about short circuit.

its not accessory to change all i got once problem but only one driver was burn but still there is no guarantee try to change one also some time main board also can be fried so you need to start from one to replace

My case is the heat bed connector was melted and short circuit the heat bed output. I don't know how could that happen.
So right now I just remove the connector and soldering the wire on board instead.

I received my printer this week and Sunhokey has now added M4x8 screws in a bag with a warning note to use those to mount the PSU.

Yep, when I received my printer I reminded them once again and proposed they put in a warning note. Maybe they listened to me now or some other customer that reported back.

Below the message I send.

Just a warning about the PSU mounting, because the screw are a bit long they can touch the 12VDC rail so shorting the AC ground with 12V. See also http://www.thingiverse.com/groups/sunhokey-3d-printer-owners/topic:2469 and http://forums.reprap.org/read.php?406,523730 Put in a warning note with the kit or better adjust the mounting video will prevent you from having a bad name and save you some money by not having to refund MKS boards or repairs.
Further I want to say it is a really nice kit for the money and me and my son love using it and experimenting with our first steps into 3D printing. I still have to write my review on aliexpress, which will be positive and also to inform people to look out when mounting the PSU.
Lucky I saw some reports about the blown boards, so I was carefull not to use the USB until I found the mentioned topics above. I now have some spacers between the PSU and the acrylic and have no problems with connecting the USB.
Thanks in advance for reading and taken notice of the above issue.

I received my kit today and, being aware of this thread, noticed a an extra little bag of M4*8 screws with a thin strip of paper enclosed that reads:

"Attention:fasten the power supply in the acrylic part with M4*8 screw"

So at least it appears that the feedback is being heard. I've only just started building and can attest that some simple assembly diagrams would be infinitely more useful than the video.

Thanks for the info - I think my motherboard just blown up because of this issue; i'm going to measure grounding right now, but I think it'd already too late for the electronic.

Well what a coincidence, I was going to post a warning regarding that very problem. I took one look at the bolts, then the power supply and decided to use standoffs then move the power supply away from the sheet of Acrylic so the air vents weren't compromised, but my standoffs were the wrong thread.

What I ended up doing was put one M5 nut on the M4 bolt between the acrylic and power supply. A little fiddy, but when I finally managed to get them all in the supply was clear enough to allow plenty of air into those vents, plus there was no hope of the bolts causing a short.

Actually 3 of the 4 bolts could come in contact with the PCB, a very dangerous situation. You're lucky one of them didn't make the supply casing live. Another "could be" problem I saw was the excess of wire used in the build. Long lengths of small diameter wire can show too much resistance, especially with the Hot Bed heater and Hot End drawing a lot of current. I spent an afternoon shortening every wire on the printer. The end result is a lot neater too. Combine those two problems and it's no wonder other guys were getting blown power supplies and that of course could lead to blown controller boards.

I suggest anyone with a Prusa I3 checks their setup to ensure they don't have an accident waiting to happen. Spread the word to any newbies about to start building too. Thanks Francisco, a good find.

Yes I just discovered that it is still 12V on ground when removed the one - can you say what 3 screws are this?

I wouldn't worry about which 3, isolate them all. To find out I'd have to dismantle mine. As I used M5 nuts on m4 bolts it was a fiddly task to get them fitted. I'd recommend using M4 standoffs if you can get some, failing that use the same m4 bolts with m4 nuts, a lot easier to fit :-). Avoid using shorter bolts because that means you will be blocking the air vents on the underside of the power supply. ... Stu

Haha snap, same here :) See my post below. I put a comment on aliexpress about it as have others.

This group is not easy to find so its important to tell the vendor - and add the information to a review if you can.

Had also an issue with Cura, heating fan just stop to work i don't know why, i've this issue only with Cura, things is working fine with Repetier.

I used the spare M5 nuts supplied as washers/shims to reduce the amount the M4x12mm screws penetrate the power supply housing.

Thank you very much Francisco and Hastla for the warning... I already pinned this thread.

Could you change the title like "ATTENTION!... SHORT CIRCUIT/FIRE HAZARD - VERY DANGEROUS"

Hope NO more incidents like this ever happen.


Hi hastla

Here is an image of the screw i am talking about.

Measure the ground of your PSU against the ground of the USB connector in the breakout board with a Voltmeter, if you found a short circuit, then you have the same problem with your 3d printer.


Thanks Francisco! Danger avoid.

THX! This topic should be pinned... can be really dangerous.


had the same issue & didn`t find an answer for it - can you please post a pic what screw is "bottom right".
I will have to look at it and fix that too as I had no idea why this happen. Thanks!

Replace them all Hastla, 3 of the four can come in contact with the PCB tracks.

I can confirm this is still a problem, just received my printer and the mounting of the PSU and instructions are still the same. So be aware.

My prusa i3 came with a sticker warning about using the correct screws and had an additional bag taped to the psu with the correct screws. The dvd still had the wrong screws listed however so be warned