Please help - burned USB port on MTCC

[mrtowel]

Hi,
I bought a USB camera for my head unit (MTCC-KLD6-V2.91) from AliExpress, connected it (using a USB port which gets the power from the car, while the data gets into the head unit), and got a picture . After few seconds, it suddenly disappeared, so i did what i thought was wise - and tried the a different USB port (which gets the power directly from the head unit), but no still picture (i said - ohh well, cheap camera)

Trying to understand if that's a camera or a headunit issue, i tried to connect it to my PC, which happily was more sophisticated than the head unit, and notified me that the USB port is trying to consume too much power and got disconnected, well - that's a bummer! try to connect it again through a USB current meter - and it was shut down immediately - turns out the USB connector was defective, and when bent, was shortening the power lines.

I cut it out - replaced the connector, and got the camera to work (on my PC), but i wasn't so lucky with the head unit or the power adapter connected to the car, both aren't working anymore (the head unit works well - only the USB port isn't)

So I opened the head unit (hoping to see some burned fuse) - but no visible damage

Does anyone have an idea where/what to look for?

[ I'm not sure if the forum rules allows me to post link to the product i bought - but if anyone interested, message me and i'll be happy to share the link]

Thanks.

 

[ZelenyR]

Burned USB

Hello, could you switch ON your WiFi interface on this headunit? Please send me a link to your headunit type. Maybe i can help you. BR Radek

 

[mrtowel]

Hello, could you switch ON your WiFi interface on this headunit? Please send me a link to your headunit type. Maybe i can help you. BR Radek

i'm not sure i follow...
the device works well, everything but the USB port seems to not be affected by the shortage (so yes - i can turn on the wifi interface).
my device is :
MCU version：
MTCC-KLD6-V2.91
May 31 2016 19:54:14
Android version：
5.1.1
1024*600
Kernel version：
3.0.101+
[email protected] #11
Thu Jun 30 11:25:16 CST 2016
Build number：
rk3188-userdebug 22062016.17:05:11

 

[ZelenyR]

burned USB

One day before I repaired one headunit with same issue and also reason of defect was same - high current from 5V supply on USB interface . Repaired MTCC has also another symptom and it was WiFi issue - when I tried to switch on WiFi interface system after few seconds switched it OFF. The reason is very simple - on that MTCC was supply of WiFi module connected to same 5V as USB ports.
5V on your mainboard will be probably generated by switching supply source and its current capability is bigger than 4A but this supply voltage is distributed to many subsystems and each trunk is switched by MOSFET. In my case weak point was inductor connected between 5V power supply and switching MOSFET. This inductor was burned by overcurrent . I think that in your case it will be similar. It is necessary to find path on PCB between supply source and +5V USB pin and on this path will be probably burned inductor. All is highly dependent on type of used mainboard.

BR Radek

 

[dhmsjs]

Attached is an annotated image of my Klyde main board labeled KD-HCT-MB 2015/07/18 Rev-3.1 1535. The two switching regs on the right are controlled by the MCU; the upper one (U25) supplies the USB hub through transistors (Q8 & Q9) which are controlled by MCU pin 38. On my board there is an inductor (L14) near the USB device (U11) which supplies power to it. If you have a similar main board, that may be your inductor.

 

[ZelenyR]

Burned USB

Hello, this is exactly picture of my repaired PCB. Inductor close to USB is used for separating path used for supply WiFi module ( there is 3.3V LDO supplied after MOSFET switch from this path close to WiFi). I don´t remember exact number of inductor but in my case was burned L16 ??? which is located on your PCB in group of components is on left side of the MCU under video switch, in middle of line of component above two electrolytic capacitors. This inductor is connected directly to 5V switching supply on one side and on oposite side is connected switching MOSFET which provides supply to USB ports (here is connected other inductor close the big black multiconnector).
BR Radek

 

[dhmsjs]

Hello, this is exactly picture of my repaired PCB. Inductor close to USB is used for separating path used for supply WiFi module ( there is 3.3V LDO supplied after MOSFET switch from this path close to WiFi). I don´t remember exact number of inductor but in my case was burned L16 ??? which is located on your PCB in group of components is on left side of the MCU under video switch, in middle of line of component above two electrolytic capacitors. This inductor is connected directly to 5V switching supply on one side and on oposite side is connected switching MOSFET which provides supply to USB ports (here is connected other inductor close the big black multiconnector).
BR Radek

Yes that group also includes the Q8 and Q9 I mentioned.

 

[shisamo]

my device is :
MCU version：
MTCC-KLD6-V2.97

Android version：
5.1.1
1024*600
Kernel version：
3.0.101+


it is completely happened the same to me. When I did install my head unit it did have a smoke came out from my head unit look like something burned inside which look like burn by over current and then my wifi cannot work.
But can i ask how can test which compontent is broken and even i find out how can i replace it.
Look like the all the compontent is surface mount.

Thanks a lot.

 

[santibiotico]

Help!!! USB short circuit - USB and WiFi not working!

Hi

I have a similar issue. When cabling my car with a USB cable connected to my MTCB head unit I accidentally created a short circuit. I could see - and smell - the smoke.

The USBs and the WiFi are NOT working now. Everything else still works.

There is no signal at VCC pins in the USB ports and the WiFi is not working, so I presume the issue can be similar to what @ZelenyR and @dhmsjs described.

My board is a KGL-A90-MAIN-v06.1 - slightly different from @dhmsjs 's one.

I am posting the links to two pictures I just took - (sorry, the system won't let me attach them or add a link)

- Pic #1 (imageshack.com/a/img922/9544/VQeiqx.jpg). It shows the whole board, as a reference
- Pic #2 (imageshack.com/a/img924/4956/pfTsmB.png). It double-clicks into what I understand as the potentially faulty groups according to the info in this thread. I can't see any clear evidence of a burnt component; I can however notice some possible damage signs in the MOSFET (A79TF) (in yellow in the picture, look at that form of a 'bubble' in the middle of the component), but I am not entirely sure the component is damaged. The inductors L10 and L19 show continuity when measuring their resistance as well.

I would start replacing the MOSFET and - possibly - the inductors. Could you please help me:

(1) What type of SMD inductors do I need to use?
(2) Any idea looking at my board?

Many thanks!

 

[dhmsjs]

...I can't see any clear evidence of a burnt component; I can however notice some possible damage signs in the MOSFET (A79TF) (in yellow in the picture, look at that form of a 'bubble' in the middle of the component), but I am not entirely sure the component is damaged. The inductors L10 and L19 show continuity when measuring their resistance as well.

I would start replacing the MOSFET and - possibly - the inductors. Could you please help me:

(1) What type of SMD inductors do I need to use?
(2) Any idea looking at my board?

Many thanks!

Given that the lnductors show continuity they are probably okay; I wouldn't try to replace them. Yes the MOSFET may likely be blown, especially if it has a "bubble" on it. That's what I would replace first.

 

[mrtowel]

Finally got to try and fix my unit

after trying all kind of 'external' fixes (such as getting USB to work by connecting an external 12v to 5v converter - which was faulty and caused my canbus decoder to always get 12v on the ignition wire - and yes, i tried to pull 12v from the canbus decoder ignition wire), i decided it's time to try and fix it in the right way.
i followed your advice - and found a path to the USB Vcc wire from the 7805 regulator, and i was kind of surprised - i have 5v (well, almost, 4.8) on the USB output, I connected some USB device - and the voltage dropped to 1.3v.
i narrowed it down to some component before the USB output, which has 5v on on end, and 4.8v on the other end, when i connect a USB device - the voltage on the 5v end stays 5v, but dropped to 1.3 on the other end - so i guess, eureka?
Now i just need to understand what is this component - where to get a replacement one and how to replace it (see attached image)

can you help identifying the component?

Thanks.

 

[dhmsjs]

...can you help identifying the component?

Your board is different from mine, but very similar. On my board that component is labeled "L2" I think, although the printing is very poor so I can't be sure.

If yours is labeled L-something, then it is most certainly an inductor. They should normally have a very low resistance (a few ohms at most) and from the behavior you describe it sounds like this one has a fairly high resistance. So an easy check to confirm that would be to measure the resistance of the part with an ohmmeter. A high resistance would confirm that it is damaged.

As for replacement, I suspect that this is another case of a noise filter -- its purpose is to block electrical noise from the outside world from coming into the unit. But the only way to know for sure would be to draw out the whole circuit from 7805 to the USB port.

If it is just a noise filter then its value is probably not critical (any value of inductance is better than none), and for a test at least, you could just try jumpering across it. If that jumper gives you a solid 5v on the USB output, then that would also confirm that the inductor is the cause of your problem.

Make sure that the device you use to test the USB does not use much power! For instance your camera is probably not a good choice for testing.

 

[mrtowel]

Your board is different from mine, but very similar. On my board that component is labeled "L2" I think, although the printing is very poor so I can't be sure.

If yours is labeled L-something, then it is most certainly an inductor. They should normally have a very low resistance (a few ohms at most) and from the behavior you describe it sounds like this one has a fairly high resistance. So an easy check to confirm that would be to measure the resistance of the part with an ohmmeter. A high resistance would confirm that it is damaged.

As for replacement, I suspect that this is another case of a noise filter -- its purpose is to block electrical noise from the outside world from coming into the unit. But the only way to know for sure would be to draw out the whole circuit from 7805 to the USB port.

If it is just a noise filter then its value is probably not critical (any value of inductance is better than none), and for a test at least, you could just try jumpering across it. If that jumper gives you a solid 5v on the USB output, then that would also confirm that the inductor is the cause of your problem.

Make sure that the device you use to test the USB does not use much power! For instance your camera is probably not a good choice for testing.

Eureka indeed, i soldered a jumper instead of the faulted inductor, and everything seems to work
do you think i better solder a replacement? or i'm all good with a simple jumper?

 

[dhmsjs]

Eureka indeed, i soldered a jumper instead of the faulted inductor, and everything seems to work
do you think i better solder a replacement? or i'm all good with a simple jumper?

Congrats! The designers put that inductor there for a reason (why add the cost otherwise?) so a jumper is probably not the best solution. But if it works for you, that's what matters most. It's your choice which way to go.

 

[mrtowel]

Congrats! The designers put that inductor there for a reason (why add the cost otherwise?) so a jumper is probably not the best solution. But if it works for you, that's what matters most. It's your choice which way to go.

I'm sure it's there for a reason, i'm just wondering what's the expected impact by not having that? less resilient to "noisy" USB devices? for me it actually protected the rest of the circuit from the over current.
if i'd like to replace it, what should i get? there is no indication of what exactly the value of it (in whatever unit inductors are measured)

 

[dhmsjs]

I'm sure it's there for a reason, i'm just wondering what's the expected impact by not having that? less resilient to "noisy" USB devices? for me it actually protected the rest of the circuit from the over current.
if i'd like to replace it, what should i get? there is no indication of what exactly the value of it (in whatever unit inductors are measured)

Not USB devices so much as noise from the car's electrical system (spark plugs for example). Automotive environments are notoriously bad places for electronics to live in happily.

The units of inductance are "henries" or in this case microhenries. No way to tell the value now and I don't have a suitable meter so I can't measure mine. But again the value probably isn't critical, and any inductance is better than none. If you do want to replace it a good first order approximation might be to find one that is physically the same size. Pick one that's toward the upper end of the inductance range available for that physical size and you'll likely be fine.

 

[mbchaves]

Thank you so much... I fixed my wifi issue

Hi Guys, I've been reading this thread and fixed the wifi of my head unit MTCC-KLD6-V2.86... Like all here, all of sudden the wifi wouldnt switch on... After opening the unit and examining the main board, the L19 inductor was burnt (charcoaled ). As my electronic skills are very basic, I did what someone did here - to jumper the failed inductor and Voila!!! the wifi is back on working. I know there's a risk with this and simplest solution is not to use the USB cable that comes with the unit. I am happy with accessing internet via wifi/hotspot.. Hope this helps someone out there.

https://drive.google.com/open?id=0BzVz3275lE4aN3RNUGlpTE5rZVlXWmowckhGbHRtbm5PNGhz[/URL]

https://drive.google.com/open?id=0BzVz3275lE4aNmFZQWx0ZVB1NkxiT2cxZ0V3SUVUaFRBLVNj[/URL]

---------- Post added at 07:54 AM ---------- Previous post was at 07:49 AM ----------

Hi Guys, I've been reading this thread and fixed the wifi of my head unit MTCC-KLD6-V2.86... Like all here, all of sudden the wifi wouldnt switch on... After opening the unit and examining the main board, the L19 inductor was burnt (charcoaled ). As my electronic skills are very basic, I did what someone did here - to jumper the failed inductor and Voila!!! the wifi is back on working. I know there's a risk with this and simplest solution is not to use the USB cable that comes with the unit. I am happy with accessing internet via wifi/hotspot.. Hope this helps someone out there.
"https://drive.google.com/file/d/0BzVz3275lE4aN3RNUGlpTE5rZVlXWmowckhGbHRtbm5PNGhz/view"

 

[iceblue1980]

Good info here