An ink jet system printer of the charge amplitude controlling type prints a desired symbol in a dot matrix fashion on a recording paper. Dots for forming a column of the dot matrix are formed in an up and down manner in order to increase the distance provided between two adjacent travelling ink droplets. When a first ink droplet is directed to a dot position higher than a dot position to which a following ink droplet is directed, the positions must be separated on the recording paper by at least a first deadzone of a first dimension. When a first ink droplet is directed to a dot position lower than a dot position to which a following ink droplet is directed, the positions must be separated on the recording paper by at least a second deadzone. The second deadzone is shorter than the first deadzone.