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6 USB Charger Repaired

By Jestine Yong on October 24, 2018

My good and also electronic educated friend Erik asked me to examine his 6 USB charger. Of which he assumed it had some sort of short circuit inside why only 5 of the 6 USB charger outputs worked. Next photo shows the apparently overheated plastic cover with now defect output number 4.

After I had removed the glued on back cover using my great bag of SANHOOII service tools I easily could remove the mainboard with the power supply of which its connector pins slide into the front display panel board connectors that also had the six USB output connectors on it.

And because the power board looked okay I removed the front panel board with the 6 USB charger outputs and the display board on it by removing the 2 small screws inside.

Next photo shows the front side of that board. And the front side looked okay so I examined its component side.

Previous 2 photos of the front panel display board on component side showed the 2 connectors where the 4 and 6 pins of the power board plug into. And the reason why USB charger port 4 didn’t work anymore is visible on previous photos that show a burned R4 (just above resistor R8, see red marked square). The value measured with my Blue ESR resistor tester on the other 5 good resistors was just about 0.1 Ohm, which matches the SMD code for R100. R4 was an open connection. Obviously not because of an internal short circuit but likely because of an external over-current event that had happened. Following photos show the component and solder side of the power board.

The controller on the power board was a type OB2269CP controller. What type the primary side mosfet was could not be read because of the way it was glued to the primary e-cap and cooler plate.

The secondary power board side had two semiconductors type CX158 B20100G AKA next to 5 low ESR max 105 degrees Celsius 10V 1000uF e-caps.

Previous photo on the right showed the optocoupler in the middle with on the left the secondary side and on the right the primary side with the Tank capacitor and the mosfet. And the 4 and 6 connector pins are shown that plug inside into the Display panel board with the 6 USB output connectors. After I had replaced the bad R4 resistor I screwed and also glued back with my hotmelt pistol the Display front panel to the inside front case. This way preventing any outside force from possibly damaging the Display print when connectors are constantly plugged in and out. And I did the same by hotmelting the plastic back cover onto the case after I had re-installed the power board into the front Display board connectors. So also making sure it was still safe when the 230VAC power cord was plugged back into the power connector on the back of the case cover.

After closing the charger case I tested all outputs including previous defect output 4. And the repair like very often before only took some time to disassemble and re-assemble the unit safely back in its housing. Next photo of the USB charger clearly shows that also output 4 is fixed and working like new again!

Afterwards I phoned my friend that there most likely originally was nothing wrong with the device itself. Because most likely the problem was caused by an external device that simply used too much current somehow. Why SMD resistor R4 with value 0.1 Ohm was blown open. And I guess that with this value the current never got higher than about 2 Amps even if the value of R4 with Ohms law will limit to max 50 Amps. (5V / 0.1 Ohm = 50 Amps).

On last photo the power cord connector insert on the back of the charger is visible with the intact primary fuse on its left. With some hotmelt I also glued that white power cord connector firmly onto the power board pcb for extra stability before closing the back cover with also hotmelt glue. Another successful repair finished at no high cost whatsoever again!

Because these 0.1 Ohm R100 SMD resistors apparently are not easily found on most old spare part boards in my ‘collection’ of used electronic boards, it now was time to order a couple of them online. In case another charger board needs fixing with these short circuit protecting resistors.

Note:

My friend told me that the specs of his charger on the outputs were for a current of 3.5A max.

So according to ohms law R output USB total is 5V/3.5A = 1.43 Ohm including the internal 0.1 R100 over-current protecting series sense resistor. R100_U4 power dissipation max therefore normally would be only P = I^2 x 0.1 Ohm = U^2/ 0.1 Ohm = (((0.1 ohm/1.43 ohm)x5V)^2)/0.1 ohm, which gives 1 x 1.225 Watt or 1225 mW. When a maximum voltage of 0.35V is measured over R4 at a DC current of 3.5A. Any abnormal longer increase of current will blow that resistor to kingdom come as it has.

Without those R100 series resistors the output current won’t be correctly measured and shown. From the voltage measured over the 0.1 Ohm resistor(s) the right output current is calculated by the microcontroller on the display board and accordingly shown in any of the 6 separate current values for each output on the display.

Albert van Bemmelen, Weert, The Netherlands.

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Note: You can read his previous repair article in the below link:

https://jestineyong.com/interesting-motherboard-repair-that-you-should-not-miss/

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20 Comments

Parasuraman S

October 24, 2018 at 10:30 pm

Everything was getting easily digested by me in your article, until the tough nuts of arithmetical calculations started. Then I bunked, and allowed the whole thing to go over my head! (LOL)

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- Robert Calk Jr.
  
  October 25, 2018 at 11:07 am
  
  Mathematics is our friend, Parasuraman. A little math can keep us from burning stuff up.
  
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- Albert van Bemmelen
  
  October 25, 2018 at 2:45 pm
  
  I'm sure they only looked hard to digest because of the many ( and ) used in the formula for P = Power = U^2/R. Which equals to I^2 x R. And U over R is just the 0.1 Ohm/1.43 Ohm part of the 5V USB out voltage which we can substitute in the U^2/R formula. Which maybe was the most difficult part to digest. The total output resistance of 1.43 Ohm was found out the formula 5V/3.5A of which internal serie current measure resistor R4 with 0.1 Ohm is part of. Which also means that at max current of 3.5A the greatest part of U out will be lost over R4 which is 3.5A x 0.1 Ohm. And U output will just be about 0.35V less than 5V = 4.65V. At lower currents the USB output voltage will always be higher upto about 5V.
  By-the-way: the photo that showed that output 4 was no longer defect was taken when R4 was only bridged over because I found no R100 replacement smd resistor. And that is why the USB charger display didn't show the 12 mA current that the external USB tester showed. But after R4 was replaced with a new R100 both displays showed the measured output current.
  
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Robert Calk Jr.

October 25, 2018 at 5:55 am

Nice work, Albert. Thanks for sharing the repair with us.

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Albert van Bemmelen

October 25, 2018 at 3:00 pm

I wondered Robert, if the powercord plug on this USB charger also exists in other countries like in the USA? I guess because of the 100 to 240V AC input voltage the charger allows that it is an universal powered charger and not just our European model charger.

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- Robert Calk Jr.
  
  October 25, 2018 at 5:37 pm
  
  Yes, I have seen that type of plug in many devices.
  
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  - Albert van Bemmelen
    
    October 26, 2018 at 9:09 am
    
    Thanks for confirming Robert. I've never been in the USA to have seen those power cords. The front of the box already suggested that only the other end of the power cord that plugs into the power wall socket is different depending to the country of destination. I may have noticed that Jestine at Noahtech center occasionally also needs a few conversion power wall adapters to be able to use certain devices.
    
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beh

October 25, 2018 at 3:45 pm

Nice repair and thanks for report.

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Albert van Bemmelen

October 25, 2018 at 4:34 pm

Thanks Beh. These chargers are well designed but I think just the current measure resistors are a bit under-dimensioned wattage wise.

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Abraham

October 26, 2018 at 1:19 pm

Thanks for helping us have a nice time

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- Albert van Bemmelen
  
  October 27, 2018 at 6:34 pm
  
  Thanks Abraham for your kind reply. Have a nice time too!
  
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Yogesh Panchal

October 31, 2018 at 2:38 pm

Albert,

you are right; finding low ohm resistors is headache"""" good if you keep some junk boards for this type of repair.
thanks for the article.

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- Albert van Bemmelen
  
  November 1, 2018 at 1:29 am
  
  That is why I ordered 50 of them through Aliexpress for about 1.90 Euro. But I find that lately Aliexpress provides bad service to me after sellers frequently had cancelled my orders after they already had been paid. And some sellers keep lying to me that I need to wait a couple of weeks more after already was waiting for 2 months on a by the seller 2 months ago cancelled parcel! It sadly means that the buyer protection is a big lie on Aliexpress because I never got that buyer protection and neither got those parcels I ordered! Also because it happened that the Aliexpress screen scrolled over an item I was trying to confirm when the wrong order popped into place and was confirmed being received instead. After I explained it to the seller who then cancelled my order after I had paid him already and Aliexpress kept ignoring my complaint that I had never received my order. Including the fact that some sellers on Alie sold me very dangerous and incomplete Li-ion charger boards. And after repeatedly having opened their online Chat service they never refunded or helped me to receive my products which really stinks!
  So I will buy less from them and use Banggood, eBay and other providers instead because Alie's buyer protection is a big HOAX!
  
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Gerald Musy

November 3, 2018 at 9:02 pm

Hi Albert, good information thanks for sharing.

btw what are the SANHOOII service tools? Sorry for my ignorance 🙂

Your article is particularly relevant for me because I ordered one of those 6 USB chargers (same model) and was interested to see a bit inside before I get it.

Not sure if this post is still open but I try
Cheers,
GM

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Albert van Bemmelen

November 4, 2018 at 1:25 am

No problem Gerald. The SANHOOII service tools mentioned are this 38 in 1 set ideal for opening all sorts of devices, see this link: https://nl.aliexpress.com/item/38in1-Smart-Cell-Mobile-Phone-Screen-Opening-Repair-Tools-Screwdriver-Plier-Pry-Disassemble-Tools-set-Kit/32616390550.html?spm=a2g0s.9042311.0.0.27424c4d8PlphO
Not cheap but very helpful for opening IR remote controls etcetera. Cheers, Albert.

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- Gerald Musy
  
  November 4, 2018 at 9:16 am
  
  Thanks Albert
  
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Humberto

November 7, 2018 at 12:55 am

Fantastic your repair. Keep sharing them with us. Have a good day.

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- Albert van Bemmelen
  
  November 13, 2018 at 2:28 pm
  
  Have a great day too Humberto!
  
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Albert van Bemmelen

November 12, 2018 at 9:23 pm

Thanks Humberto. In the meantime I have received the 1 Watt R100 smd resistors. They were the only ones I could find to order. But they are much too large in compare to the original R100 resistors that are used in the charger. So it indeed means that the original smd resistors are way too small to survive big loads at 3A. And most likely the reason that the one on USB port 4 already had blown up.

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Albert van Bemmelen

November 12, 2018 at 10:16 pm

PS: On Aliexpress one seller kept lying to me that my item was shipped after he simply cancelled it after I already had paid him and now after almost 3 months still has not send me anything! Why I will mention him here to also warn others for his bad unfriendly business. And also warn for the bad Aliexpress Buyer protection that only protects corrupt lying sellers like : Leo Y from Edal Intelligent Store! And another bad seller to watch out for is the Oh!Susana'Gift Store that sold me incomplete and dangerous 30A 3S Li-ion Polymer boards that caused two cells to explode while they were charging! I have asked aliexpress at least four times to step in after I could prove my parcel was cancelled, but they ignored the fact that I never could have received my parcel! So better watch out for all transactions you do on Aliexpress because they have a very bad service policy! I therefore in the meantime blocked both sellers from my list and I am no longer ordering Li-ion charging boards from Aliexpress!

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