I was looking at my C64 Mini board and was thinking where do they go,cos mind don't work so it has to have resistors before it goes into the CPU,now If I could find out what resistors then and where I could try to replace them,but that would be very hard cos of how small the board is.
Here a picture of the Uart connector..
and here is the back of the board at the same place..
and another picture at a different angle..
Here is the schematic of the A20-OLinuXino-Lime board that this board is part copy of.. just the Uart part..
The TX/RX lines appear to go directly into the CPU. It seems that you may have burned one of the traces, on the 2nd from the right. There's not much you can do to fix it except maybe scrape away some of the protective layer and lay some fresh solder on it unless you burned it all the way to the CPU which is possible as well.