1. Disconnect the HP Deskjet 3840's power cord if the printer does not start up when you press the "Power" button. Wait at least 10 seconds for the printer to reset itself and plug it back in. Press the "Power" button and wait as the printer starts up
2. Pull out the HP Deskjet 3840's paper tray and ensure that the green paper alignment tool is pressed firmly against the sheets of paper. This will prevent your printed documents from coming out off-centered.
3. Replace your HP Deskjet 3840's black ink cartridge with a photo cartridge if your printed photos are fading near the edges of the paper. Additionally, go to your computer's taskbar and right-click on the printer icon. Click on the "Printer Properties" tab and then click "Paper/Quality." Click the "Print Quality" button, check off the "Maximum DPI" box and close out the screen. Reprint your photos.
Article from : ehow.com