An ink jet recorder of the continuous jet type has a mounting block (3) defining a reference surface. Nozzle units (1a-1d) from which the ink stream (5a-5d) are ejected are releasably keyed to the reference surface. An ink reservoir supplies electrically conductive ink to the nozzle units which selectively charge segments of the ink streams issuing from the nozzle units. Each unit also includes provision (91, 93) for accurately aiming the ink stream in both the x and y directions using simple knob controls. A deflection unit (7) is also releasably keyed to the reference surface downstream from the nozzle units. The ink stream is directed through a deflecting unit (7) mounted on the reference surface. Mating members (140, 141, 144) (146, 148, 150) are provided in said mounting block (3) which corresponds with mating members on the deflection unit. This unit generates an electrical field which deflects the selectively charged segments of the ink stream issuing from the nozzle unit, from their predetermined paths so that they do not reach the recording medium; the undeflected portions of the ink streams form the printing on the medium. The deflection unit also includes provision for removing extraneous ink from the regions of the deflection field so as to minimize background coloration in the printing on the medium. A charged mist shield (126) is provided in said deflection unit to further attract extraneous ink in and about said deflection unit. Vacuum means (13) are provided to withdraw extraneous ink from said deflection unit, nozzle unit, and mist shield.