The backlight on my Asus Transformer broke and i need to send it in for repair. I bought the tablet used already rooted. I have no idea which root it is, and I can't see anything on the screen. I tried unrooting using the method provided here, but it didn't detect my device. Also it won't go into APX mode and I can't see anything that's happening on the screen. I was thinking I could connect the tablet to a TV, but I don't want to purchase an HDMI cable before I have a sure method that will unroot my tablet. The serial starts with B6O, and since it's the backlight that's broken I can still see very limited parts of the screen.
Here I found a detailed description how to unroot your Asus TF101 transfomer.
The procedure is not trivial and you need to follow several step, but most of them can be done through adb so there are chances that you can do it.