hp deskjet 940c

[Not_a_Geek_WI]

I'm using an HP deskjet 940c.  It prints fine except there is a vertical "line" in the middle of each page which contains doubled characters in lighter type, sort of like gosts of the first character.  These always start on each line toward the middle of the page (but not always exactly in the same spot) and run for about 10 characters.  Then printing is back to normal.  I've tried cleaning the cartridge port head and the cartridge head and have replaced the cartridge.  No luck!  Troubleshooting through the computer indicates there is no identifiable problem.  I've tried rebooting everything in varying combinations.  I've tried printing things from different programs (word documents, emails, etc.)  Always the same ghost letter result.  I ran the Window Printer Test Page which reported that the 940c was correctly installed.  It ran out a list of additional print driver files which is the only thing that ran into the middle of the test page.  The letters toward the end of the file name reached the middle of the page and had ghost letters.  Anyone seen this problem before?  Thanks!

[Bob_Headrick · Accepted solution]

The issue you are describing is one that could be caused by ink aerosol fogging the encoder strip used by the printer to keep track of the carriage position.  

You might try cleaning the encoder strip as shown in the post here.  The encoder strip is fragile, please read and heed the warnings.  Only use water to clean the strip, not alcohol or any other solvents as the fine lines printed on the strip are needed for proper operation of the printer.  Be gentle!

[Not_a_Geek_WI]

Cleaning the encoder strip was exactly the solution.  Thank you very much!