If your printouts contain misaligned vertical lines, or you see light or dark horizontal banding, you may need to align the print head.
Macintosh OS 8.6 to 9.x: From the File menu, select Page Setup or Print. Click the
Utility button, then click the
Print Head Alignment button.
Macintosh OS X: Open the Applications folder and select EPSON Printer Utility. Select SP 900 in the printer list, click OK, and select Print Head Alignment.
Select one pattern each for rows 1 through 3. Enter the number of the best pattern for each row in the corresponding boxes on the screen. Then click Next.
If you can't find an aligned pattern, choose the one that's closest to being aligned. Then click Realignment to print another test page and repeat this step.
If you can't find a box that doesn't contain banding, choose the one that looks the best. Then click Realignment to print another test page and repeat steps 6 through 11.