So I bought it on ebay.
And the very first time I plugged the usb in, the power led barely light up, it was very dim and the PC won’t recognize it.

On the other hand, when I connected it with the DC jack it was working perfectly.

So i took my multimeter and traced the power lines from the USB and where they break, and found out one of the diodes was bad, so I replaced it, but I didn’t have a surface mounted diode, so I took a regular one … watch the video :

The outcome: