I just got this today, plugged it in my arduino, and the arduino light starts dimming until you cannot see it any more over the course of 5 seconds. The Computer disconnects the arduino when the light is off (Ding Dong Sound). I found pulling the VIN Connector Jumper/Power Jumper will stop the short circuit and work, but that defeats the purpose, as the board wouldn't even powered.
Here is the video: YouTube
Is the motor board broken? If so in what way? are the wires on the board simply broken? Is it due to bad soldering?(I checked solder, looks fine).
Arduino Model: Arduino UNO by Elegoo Motor Driver Model: L293D Driver Board Ebay Listing For Item (I tried using this with a MEGA also, would short it as well).