If the ink has run out and the print heads are dry, you may manually clean your Hp Envy 5660 printer's print heads. Use an isopropyl alcohol-soaked Q-tip to carefully wipe away any dried ink that may be present on the printhead in order to do this. But if you don't do this regularly enough, your print head can become damaged or perhaps cease functioning entirely. This may result in poor-quality copies printed on inferior paper and printing problems.