An ink jet system printer of the charge amplitude controlling type includes a carriage travelling across the printing region. A nozzle for emitting ink droplets and a slidable member are disposed on the carriage. The slidable member supports a charging tunnel and a cleaning pad for cleaning the front surface of the nozzle. When the carriage is positioned at the leftmost position before initiating the actual printing operation, the slidable member is slided on the carriage so that the cleaning pad contacts the front surface of the nozzle for cleaning purposes. Thereafter, the slidable member is held stationary on the carriage at a position wherein the charging tunnel confronts the nozzle.