I want to use a toner cartridge which I have in my old HP LJ2420 in my new LJ2420. The printers are identical but when I put the part used toner into the new machine it will not accept it. I am aware of the chips in HP toners and I wonder if once a toner has been installed it cannot be transfered. Has anyone experienced this, or is there a way to get the new printer to accept the existing cartridge??