PSU/PC Frying CH340G

Hi all, so I purchased a chinese 3d ctc 3d printer kit a few months ago as my first foray into 3d printing. I got it set up (the controller was essentially just an Anet a8 clone board) and it worked like a charm. One day though it started being a tad off while trying to use repetier host to set it to print, none of the temperatures were displaying correctly in repetier host. So I restarted my printer and pc, and bam, nothing. The printer stopped connecting to the pc entirely. I had no idea what I'd done wrong, other than I'd installed another serial port driver for a different project earlier that day. I just assumed that must have broken it somehow and just printed from sd card from then on. I recently however wanted to upgrade the threaded rods to lead screws for some improved z axis travel, so I thought I'd get a new controller board to go with it. I purchased a 'MKS Gen L V1.0' controller from ebay along with some DRV8825 stepper drivers. I also got some 'stepstick protectors' to go inbetween the board and steppers to allow the printer to be quieter during operation. Once all the parts had arrived I programmed the controller with no problems, without a psu or any steppers connected. But once I had assembled it I couldn't seem to upload any changes to the firmware as the board was being recognised by the pc but it couldn't be accessed. I took the printer to parts again and tried to program the board on it's own, and only when I tried changing usb ports on my pc itself was the problem fixed. I then put it all back together and could get the controller recognised when I connected it. However, if I connected the power to the board before I had connected the usb cable the board wouldn't be recognised, and if I connected it usb first it worked until the power was turned on. I tried to make sure all the cables were in the right place and even checked my psu's voltage which was a steady 11.65V. When I try to connect my board now however, with any external psu or steppers or without them, it just blinks a blue light twice then sits there while the ch340 gets warm, and the pc doesn't recognise it at all. So now I'm wondering if perhaps the damage isn't coming from my power supply but rather my pc? Does anyone have any ideas as to what's wrong here and perhaps how to right it as a hundred quid later and two broken controller boards and I'm about ready to call it quits on this whole thing. Thanks in advance