Part blew up on Prusa i3 motherboard MKS Gen-2Z v1.1

Hello all,

I got a Prusa i3 kit from Sunhokey on 3dprintersonlinestore.com, and just yesterday a tiny part labelled LG1 blew up on the motherboard. Now the heating elements and motors won't do anything, but the ATmega seems to still be intact as the LCD menu still works - leading me to believe the part had something to do with the power supply portion of the board for high-power devices. Has anyone else had this issue? I contacted the supplier, who offered a replacement but the international shipping would cost more than a simply buying a replacement. Unfortunately the damaged part is SMD, so I guess there's little hope of fixing it (especially since I couldn't find any schematics and it appears do be an off-brand). Has anyone ever tried supplementing the board with some sort of arduino mega 2650 circuit? (Would have already done this if I had the schematic).

Thanks,
Ben

Can you show us a picture of the part?
It sounds like an inline coil to damp inrush current. If that´s true, you can shorten it to make the board work again.

No guarantee
-Olaf

Olaf --

Here's a couple shots. I gave an overall shot too because it looked to me like at least part of the board was different from all the pictures I saw online. I tried to get pretty close to what's left of the busted piece (as close as auto-focus would let me). Most of the busted piece isn't there anymore (I tried to get it out with tweezers so I could expose the solder pads), but it just looked like an ordinary SMD diode or resistor and had no markings on the piece itself.

-Ben

They seem to have changed the switchmode power stage. Or is it a 24V variant?
Sorry, I can´t identify the part or anything without schematics. Where have you read LG1?
-Olaf

Nope, it's 12V. LG1 was printed on the PCB next to the part - you can barely see it in the 2nd and 3rd pictures. Still can't seem to find a schematic (or even PCB footprint) for this variant - and I've pretty much given up on help from the supplier. And I tore the internet apart looking for what LG stands for - no luck.

-Ben

Hi Ben,

I have the same issue with my Gen-2z V1.1.
Did you jet found something that solved the problem?

I'd really appreciate any help

-Julius

Julius-

Unfortunately, I didn't find a fix. I had to send it back and they repaired it under warranty but I had to pay for new stepper drivers, somehow they got damaged in the short. Too bad there's not better schematics.

Ben

Looks like a coil to me, there's a LG2 on the board and my guess is it's the same kind of part. In electronics L stands for coil. What the G represents I don't know but my guess is it's a class of the coil.
It's hard to reach and not knowing the coils induction doesn't help either. That's the disadvantage of a closed source board I guess.

Hello all,

same issue happened to me.
Do anyone know what is the part LG1 on board ?
Maybe after, replacement it could be visible some marking on it.
I do not want to buy whole new board when probably this is factory issue and it happen on new board again.
I would appreciate any help.
Thanks

My guess is that it's a SMD ferrite bead, connected in series with a power line, ie 5V. If you own a dvm, you could try to find out if it's connected to 5V (pin 1 on USB connector). The datasheet of the ft232rl chip recommends MI0805K400R-10, a 40Ohm impedence at 100Mhz. This one can handle a maximum current of 1.5A.
Please check if the size is correct, the recommended part in the datasheet is a 0805 size (2mm x 1.25mm). I can't tell from the picture above.

It still raises the question why it blew up in the first place though. You have to find the short circuit first before replacing it. It could be an endstop shorting 5V to ground, or a wiring problem etc. Measuring the 5V to ground would be a good place to start. If that shorts out then you'll have to find the culprit first.

You can also short the SMD pads, as a ferrite bead looks like a short for DC anyway, though it should only be used to confirm it's working, then replace the short with a proper ferrite bead.

I have the same problem, but in my case the SMD is still soldered to one of the sides, the other end is standing vertically. This happened after I connected USB and then mains power (I posted a topic here: [forums.reprap.org]). This somehow caused a short or whatever that also burned my PC usb ports. When board was plugged in just with mains power it was fine.
Maybe I should try to resolder this part?

UPDATE: I resoldered the part, even tried to short the 2 pads together - no luck.
In both cases after powering the board, the 5 stepper motor controllers start becoming very hot. When the part is unsoldered this doesn't happen.

I couldn't see any labels on the part... So I'll probably give up on this board and look for a replacement, unfortunately they seem to be not so cheap...

Edited 2 time(s). Last edit at 09/05/2015 11:59AM by ltomov.

the damage must be too extensive.

If you get another board you can consider getting a ramps and arduino mega 2560. They are cheaper and easier to obtain.

Quote
imqqmi
If you get another board you can consider getting a ramps and arduino mega 2560. They are cheaper and easier to obtain.

Thanks, I'll go for this option, looks like it may need some small tweaking for the connectors, but should be possible.

1. LG1 is a magnetic bead. The base function of LG1 is connecti
ng AGND (motor) and DGND (CPU), which can reduce disturbing from motor to CPU.

2.These reasons can cause the burning of LG1(may be more reason):

1) Voltage between AGND and DGND is too high. High voltage will cause LG1 over-current( MAX current is 2A), and the other parts of MKS GEN may be damaged or not. The high Voltage mostly come from some accident reason, for example: when adjusting the motor current, some accident cause A4988 drive damage, which resulting in high voltage come into DGND.

2) Power chip L5970D is damaged (Accident caused by long time short circuit damage or Switch supply power input shorted, or Switch supply power input voltage exceeds 35V), which will cause LG1 burned, and then damage other parts of the MKS GEN circuit.

3.How to do when LG1 burned:

1) Replace LG1 or direct connect the two pads(short circuit it), and then test the function.

2) If is ok, the board can be used as normal. If not ok, the board need for further repair.

4.the schematics of mks gen can be found here [github.com] : mks_gen_sch.pdf

5.the the schematics of mks gen's power circuit can be found at attach.

Edited 2 time(s). Last edit at 09/09/2015 06:12AM by flyway97.

I just build a prusa i3 from sunhokey. I am however a bit nervous connecting the USB, I have read several reports that the board blew up when having the usb and 12 volt main power connected. Can I update the firmware on the board without connecting the 12V or are there some other precautions I could take to prevent blowing it up? I am using an SDcard now to print, also have no intention of connecting it to a PC other then updating firmware.

Thanks in advance

divx118 -
Not much you can do I think - you can try only plugging in the usb and see if you can flash the firmware like that, but I don't think firmware is the issue here, but rather a manufacturing defect. I will be sending a link to this forum to Sunhokey, as I was forced to pay a large shipping fee as well as for new stepper controllers when I requested a replacement, even though I didn't cause any damage (which they didn't believe) and the warranty covers factory defects. I encourage others to do the same.

Ben

@Ben, firmware will indeed not be the issue, however I don't want to blow up my board right now that is why I am asking if there is something to reduce the risk. Just enjoying my first steps in 3D printing. You are right to e-mail them this is surely a hardware bug/failure and shouldn't be happening. Just have a look at some feedback posts on [www.aliexpress.com]

Sorry for not editing my post, but this is to imported so any subscribers to this topic will get an update.

Just found this thread [www.thingiverse.com] So check your PSU housing screws. This will only be a problem if you use grounded AC outlet on both printer and your PC nevertheless you should fix it. I measured my PSU housing and it is fine. No 12V. However I will take the screws out and put some distance between the PSU and the acrylic. I didn pay any attention to the screws before, because my son screwed it in. I checked them now and they are indeed dangerously close to the back of the print in the PSU.
I don't know if this will explain all the MKS board blow up's, but it could be a good explanation.

Edited 1 time(s). Last edit at 09/13/2015 06:15AM by divx118.

Yep, looks like that's what fried my printer. I just measured it and depending on how you twist the screw inside it may or may not reach the 12V rail. Several times I did managed to short it.
I put one multimeter end in the screw hole and moved it a bit - it reaches the 12v - no problem. There's a very thin layer of something plastic that they put there to protect the rail and I guess it's easy to get cut. Well at least the short is between earth and 12v, it could have been the 110/220v terminal... Crappy uncertified junk.
I noticed there's a CE marking on the box - I heard there are two types of CE - the European Certification, and "China Export", I guess this one stands for the latter

Hi guys, Can someone explain what and where to measure? Is it voltage or resistance?
Already burned 1 board and 2 sets of steppers .Would like to confirm this is my problem indeed.
Thanks!!!

@tow disconnect all the wires from the PSU and measure resistance between 12V output and case. If it is shorted, you probably have the screws touching the PSU board. <-- This will be the best and safest way to do. You can also disconnect the +12V and 0V of the PSU power it up and measure between 0V and the case to see if you have 12V on the case. If you have then the screws will probably touch the PSU board.

Also the short doesn't occur at all times. In my case I measured the voltages several times (with screws mounted) and it was all fine. But then it blew up.
You need to twist the screw in a special way I guess. In my PSU there's a thin layer of plastic between the screw and the board, so it may protect it sometimes, but it's very easy to cut. I was able to confirm this was my problem by giving that screw a good twist several times and seeing the short between the 12V rail and the metal case.

The problematic screw is shown here:
[s9.postimg.org]

Appreciate your help guys.Problem confirmed.Same screw ,same issue!