A diazotype copy machine including a developer unit having an applicator roller for applying developer to a copy sheet and means for dispensing a substantially uniform coating of developer onto the surface of said applicator roller including means movable toward and away from contact with said applicator roller between an engaged and a released position. Control means is provided for moving said dispenser means between said engaged and said released position and drive means is provided for normally driving said roller in one direction to make copies. Said drive means includes slip clutch means permitting free rotation of said applicator roller in said one direction relative to said drive means, and means is provided for reversing said drive means whereby said applicator roller may be freely rotated in both directions to facilitate removal of a copy sheet jam around said roller.
