Sunhokey Prusa i3 - Magic Smoke And Death After Connecting USB

Hello,

I just got my prusa i3, by some chinese manufacturer Sunhokey, unfortunately it burned very quickly
I'd like to ask if anybody else has encountered such a thing, if this is an "expected" behaviour and I've done something stupid, and hopefully some advices on how to get it back to life...
Here is the story:

I just finished putting all parts together, all the wiring seems ok, the output voltage from the power supply is 12V.
So I started testing the printer, moving the motors, clicking around the menu - everything seemed to be working fine.

Then I moved to the next step - installing the software and connecting to my laptop. And that's when fate struck its anger upon me...
It was all plugged off, I connected USB and saw the display powering on and menu working. I knew that usb power wasn't enough to drive the motors, but I decided to click around just for the fun of it. Of course they didn't move.
Then I plugged in the main power - I heard a boom and the electronics board started smoking.

I plugged off everything and plugged back in just the main power - the display and menu is ok, but the motors are no longer working. Only the fan and the display are ok.
2 of my laptop's USB ports are also destroyed.

This is not normal, right? Or is it? Did I do something wrong - like plugging the USB cable and clicking around with no mains power?

Any idea how to fix that? Can I get a new electronics board?

Thanks in advance!

Edit: forgot to mention the board is MKS Gen 2Z v1.1, the smoke appeared around the 3 capacitors behind the USB port.

Edited 2 time(s). Last edit at 09/05/2015 08:27AM by ltomov.

One interesting thing that I found is that this board is supposed to have a "recoverable fuse for short-circuit protection". But I cannot find it in the board (I'm no expert so I really don't know how it may look like). Any idea how to find it and reset it?

No it's certainly not normal and unfortunately I've seen more reports of this problem. My guess is that the 5V regulator or ferrite bead gets overheated and burned / blown up when there's a bad quality external PSU connected and the USB cable is plugged into the PC.

Could you show a picture and make and model of the PSU? It would be interesting to see if there's a certain brand to be avoided.

The poly fuse is the yellow capacitor looking thing near the connector, a small one and a bigger one.

Edited 1 time(s). Last edit at 09/05/2015 12:14PM by imqqmi.

This is the printer I got: [www.aliexpress.com]
It comes with a PSU which is the same as this one: [www.ebay.com]\
I'm not saying the ebay one is bad, but it's the same model and looks. No other markings are there like brand, just this "model sp-360 12v".

I found another topic where people have exactly the same problem, with this Sunhokey printer - [forums.reprap.org]
In my case this part also blew up.

So you're suggesting it's the PSU, rather than a manufacturing defect in the board? I was thinking of getting a new board (but maybe v1.3 as this one is v1.1), but perhaps I should get another PSU also?
It's interesting because this listing has ~1500 orders and 95% good reviews, and looking at some youtube videos they all come with a similar looking PSU... That lead me to believe it should be quite reliable, but obviously not

I guess it's a combination of factors, I've also seen a post where one pc got problems while another was ok. My own experience is that switching psus have difficulty sharing ground, and dual power is tedious at best. Server psus are of course the exception as you can find multiple in one server chassis. I think psus for led drivers don't have to interact with other psus either so may not be designed to run in such an environment.
Quality control is another issue too.

I see, thanks for the suggestions. I have an atx PSU lying around which is supposed to be of a good quality, I'll check if it can supply enough power.
And I guess next time I'll use a usb hub, in case anything goes wrong, it should be cheaper than fixing laptop ports

Or an usb isolator:
usb isolator

Sounds like this may be the cause;
[www.thingiverse.com]