Toy RC car un-findable driver IC

[Ero-Shan]

A friend of mine asked me to see if I could repair his grandson's RC car.

The fault is quite obvious:



There are 2 DC motors, each of them driven by one of the (most likely H-bridge driver) ICs. Both motors still run fine on my bench supply, drawing up to 3 A at 3.5 V. So what caused this dramatic failure is unclear.
Anyway, try as I might, I was totally unable to find anything about those driver ICs. The logo looks like '7L' to me, but that doesn't help. And the name 'MX630LE' didn't find me anything even remotely connected, either.

As much as I'd like to do my friend a favor (albeit hating these extremely annoying cars!), I'm afraid I have to tell him they'll have to trash it and buy another one (or better yet, buy some better toys ).

Just for reference, here's the 'car':



Any idea how I might repair the thing would be greatly appreciated.

[kleiner Rainer]

Found a schematic at the FCC Database:

https://fccid.io/OTM-8455118-24GRX/Schematics/Circuit-3976831

Maybe that helps find a solution.

Greetings,

Rainer

[darkspr1te]

A friend of mine asked me to see if I could repair his grandson's RC car.

The fault is quite obvious:



There are 2 DC motors, each of them driven by one of the (most likely H-bridge driver) ICs. Both motors still run fine on my bench supply, drawing up to 3 A at 3.5 V. So what caused this dramatic failure is unclear.
Anyway, try as I might, I was totally unable to find anything about those driver ICs. The logo looks like '7L' to me, but that doesn't help. And the name 'MX630LE' didn't find me anything even remotely connected, either.

As much as I'd like to do my friend a favor (albeit hating these extremely annoying cars!), I'm afraid I have to tell him they'll have to trash it and buy another one (or better yet, buy some better toys ).

Just for reference, here's the 'car':



Any idea how I might repair the thing would be greatly appreciated.

If you search google for "MX630 motor driver IC " you will see suppliers like fengsheng , can be found on ali too. not sure of a equivalent but you could replace the board with esp32 and esp motor board for super cheap if you want to hack it back to life.


darkspr1te
 

[pcprogrammer]

It is of course a gamble but here for not to much money https://aliexpress.com/item/1005003843607769.html

[fzabkar]

https://web.archive.org/web/20160912080003/http://www.mixic.com.cn/data/MX608.pdf  (MX608 datasheet)
https://web.archive.org/web/20160912041702/http://www.mixic.com.cn/data/MX612.pdf  (MX612 datasheet)
https://web.archive.org/web/20160912032002/http://www.mixic.com.cn/data/MX618.pdf  (MX618 datasheet)
https://web.archive.org/web/20120522232646/http://www.mixic.com.cn:80/admin/download/MX117_EN.pdf  (English datasheet for MX117)
https://datasheet.lcsc.com/lcsc/1810161611_Mixic-MX612E_C110207.pdf  (MX612E datasheet)
https://taoic.oss-cn-hangzhou.aliyuncs.com/7942/product/ZTAOIC_1614157843000.pdf
https://fccid.io/2AIRRINT108/Schematics/Circuit-Diagram-3627517.pdf
https://cech-krotoszyn.pl/wp-content/uploads/2021/01/Schemat-4.pdf

Mixic DC Toy Driver Series Chips:
https://web.archive.org/web/20160912080225/http://www.mixic.com.cn/data/summary_EN.pdf

[Ero-Shan]

Found a schematic at the FCC Database:

https://fccid.io/OTM-8455118-24GRX/Schematics/Circuit-3976831

Maybe that helps find a solution.

Greetings,

Rainer

I've neither heard from that database, nor did I expect being able to find anything about the circuit, even less a schematic! (Bookmarked it right away.)
It doesn't fit exactly, but is close enough. Great find, thanks a lot!

Greetings,
Ero-Shan

[Ero-Shan]

https://web.archive.org/web/20160912080003/http://www.mixic.com.cn/data/MX608.pdf  (MX608 datasheet)
https://web.archive.org/web/20160912041702/http://www.mixic.com.cn/data/MX612.pdf  (MX612 datasheet)
https://web.archive.org/web/20160912032002/http://www.mixic.com.cn/data/MX618.pdf  (MX618 datasheet)
https://web.archive.org/web/20120522232646/http://www.mixic.com.cn:80/admin/download/MX117_EN.pdf  (English datasheet for MX117)
https://datasheet.lcsc.com/lcsc/1810161611_Mixic-MX612E_C110207.pdf  (MX612E datasheet)
https://taoic.oss-cn-hangzhou.aliyuncs.com/7942/product/ZTAOIC_1614157843000.pdf
https://fccid.io/2AIRRINT108/Schematics/Circuit-Diagram-3627517.pdf
https://cech-krotoszyn.pl/wp-content/uploads/2021/01/Schemat-4.pdf

Mixic DC Toy Driver Series Chips:
https://web.archive.org/web/20160912080225/http://www.mixic.com.cn/data/summary_EN.pdf

Thanks to all of you, darkspr1te, pcprogrammer and fzabkar!
My Google-foo seems to be lacking ... While my standard search engine is Startpage, I did also try Google for this one. I also tried motor driver, H-bridge and some others, but must have skipped the winning combination.

I'll talk to my friend and his daughter tomorrow and let them decide.

Thanks again! At least, I now can demonstrate that I really worked on it.

Ero-Shan

[Hamelec]

Datasheet MX630LE
http://www.szxunrui.cn/siteimages/9904/2020122117001585.pdf
(translation in Attachment)

[Ero-Shan]

Datasheet MX630LT
http://www.szxunrui.cn/siteimages/9904/2020122117001585.pdf
(translation in Attachment)

Great! The MX630LT (most likely the LE is the same in that regard) can actually drive up to 2.5 A continuous. If blocked, the motors draw quite a bit more, though.
I've now removed the burst IC. There's still a short from the regulated 3 volts to ground. IMHO, there's no point repairing that POS.
But I did learn something about how these cheap toys work. So the time spent wasn't wasted.

Once again, thanks to all involved. Let's call it a day.

Ero-Shan

[pcprogrammer]

A big chance the three pin ic below the text on the PCB is a simple voltage regulator and got busted also. Seems to have smd markings that can be found on line.

Edit: The J3Y one is most likely a S8050 NPN transistor. Can't read the marking on the other one, and that might be a regulator.

[Ero-Shan]

A big chance the three pin ic below the text on the PCB is a simple voltage regulator and got busted also. Seems to have smd markings that can be found on line.

Edit: The J3Y one is most likely a S8050 NPN transistor. Can't read the marking on the other one, and that might be a regulator.

Yes, it is a 3 V LDO regulator. It's output is shorted (< 1 Ω to ground). Whatever is responsible for that - I simply don't care. This thing is way beyond any reasonable repair.
The whole task of the S8050 is to switch 2 LEDs.

The thermal pads at the bottom of the MX630 are not soldered to a plane on the PCB for heat sinking. That certainly did not enhance the driver's max current allowance.

[pcprogrammer]

Did you lift the LDO from the board, and if so is there still a short then?

[Ero-Shan]

Did you lift the LDO from the board, and if so is there still a short then?

Nah, can't be bothered. Even if I find the short, I have no replacement for the failed MX630.
It's dead, Jim. 

[Hamelec]

No risk - no fun: 10pcs
https://de.aliexpress.com/item/1005004037792240.html
https://www-szxunrui-cn.translate.goog/product248693.html?_x_tr_sch=http&_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=de&_x_tr_pto=wapp
https://www-szxunrui-cn.translate.goog/product664511.html?_x_tr_sch=http&_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=de&_x_tr_pto=wapp

[Ero-Shan]

No risk - no fun: 10pcs
https://de.aliexpress.com/item/1005004037792240.html
https://www-szxunrui-cn.translate.goog/product248693.html?_x_tr_sch=http&_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=de&_x_tr_pto=wapp
https://www-szxunrui-cn.translate.goog/product664511.html?_x_tr_sch=http&_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=de&_x_tr_pto=wapp

"5,92 / viel" - I have to like this.

Seriously, I returned the pieces on Sunday. They probably junked it already. But I'll ask my friend. Maybe it is still laying around, and he's feeling like it might be worth a try.

Thanks for your effort.