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6 USB Charger Repaired
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.
Albert van Bemmelen, Weert, The Netherlands.
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Note: You can read his previous repair article in the below link: