An electrostatic printing or copying device has a charge image of a form to be printed generated on a photoelectric recording medium with the assistance of a forms printing device. The forms printing device comprises a roller having a transparent cylinder which is arranged between two roller receiving flanges and a lamp tube arranged in the roller. The master copy to be imaged is applied to the transparent cylinder and is illuminated with the assistance of the lamp tube so as to be imaged on the recording medium. A drum acceptance flange is provided with a groove and a peripheral gear for a simple interchange of the roller. The roller is slipped onto the lamp tube for securing the roller in the printer. Subsequently the lamp tube, along with the roller, is rotated with respect to a housing part so that a centering roller engages in the groove of the roller acceptance flange and brings the roller into the correct position. Subsequently, the gear is engaged by a toothed wheel and the roller is brought into the correct position and locked thereat by means of the centering roller.
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