I have a HP Officejet Pro 8500 when I use the copy function of the printer I have two vertical black strips the length of the paper. This does not happen when I use the printer function from the computer. I am assuming it needs to be cleaned, I am unsure of what to clean.
More about :black streaks paper copy function print function
^+1, the ADF scanner glass needs to be cleaned. You wil find if you use the flat bed option of the scanner you wont get the lines. If you get the lines with the flat bed option then there is dust or something wrong with the scanner CCD.