My HP Pro 7780 has recently started making copies (through the feeder) with 2 large blank streaks down the middle of the page (lengthwise). I am worried that this is also happening when I send a fax as...
Does this happen when you print, or only when you copy? If you print out a configuration or user settings page, or print a page from the computer, is it also missing two vertical lines of print or is it only when you are copying?
If it happens when you print, you may need a cleaning, or you may need to replace the toner or drum cartridge. If it's an inkjet machine, there's a possibility there is some ink or grease on the encoder strip (a small belt-like plastic strip that goes through the print-head carriage).
If it only happens when you copy, test both the flatbed and the document feeder. If it happens on both then you may have a bad scanner. If it only happens when using the document feeder, you likely have some whiteout (or something) on the glass. When you make a copy in the flatbed, the scanner moves across your document. When you make a copy using the document feeder, the document moves across the scanner. In this case, if there is anything on the scanner glass (like whiteout) your copies will be missing a vertical line of print data (it could be white if there is whiteout on the glass, or it could be dark if something dark is on the scanner glass).
Usually you can lift the flatbed cover and look at the glass to see if anything is on it (usually at the left side of the scanner). Clean the glass, first with alcohol to remove the obstruction, and then with a little windex to remove anything the alcohol may have left behind.
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