accordingly four ink supply channels 514 are defined in the molding 512 together with an air supply channel 518 the air supply channel 518 supplies air to the printhead 516 to inhibit the build up of foreign particles on a nozzle guard of the printhead 516 the chassis 510 further includes a cover molding 520 that supports a pump 522 the pump 522 is a suction pump configured to draw air through an air filter in the print cartridge 504 via an air inlet pin 524 and an air inlet opening 526 air is expelled through an outlet opening 528 into the air supply channel 518 of the chassis 510 the chassis 510 further supports a first drive motor in the form of a stepper motor 530 that drives the pump 522 via a first gear train 532 the stepper motor 530 is also connected to a drive roller 534 fig5 of a roller assembly 536 of the print cartridge 504 via a second gear train 538 the gear train 538 engages an engageable element 540 fig2 carried at an end of the drive roller 534 the stepper motor 530 thus controls the feed of print media 542 to the printhead 516 of the sub assembly 508 to enable an image to be printed on the print media 542 as it passes beneath the printhead 516 it also to be noted that as the stepper.