Here are the steps to replace HP printhead CN642A and CN643A : Step 1 : Switch on the printer. Open the cover and wait until the carriage stopped Step 2: remove all the cartridges Step 3: Unlock the printhead. Remove the printhead Step 4 : Clean the contacts on the carriage. Step 5: Install the new printhead Lock down the printhead. Step 6 : Install the new cartridges. Close the cover
Reset printers and cartridge. Printers problem solving,tips, tricks and tutorial.