February 27, 2013 at 8:26 pm #21206
RB6 does control row 7 of the LED matrix, which (with the sideways matrix) is what we’d normally describe as “the second column.”
Backing up a bit, “columns” 1,2, and 3 are driven by transistors Q7, Q6, and Q5, from resistors R7, R6, and R5. If there’s a solder blog connecting those three lines together, or a break in the circuit board traces, it could cause the problem that you’re seeing. Look carefully at that area of the board, and see if you can figure out what has actually happened there. If there’s an accidental solder connection, you do need to remove it.