Xerox workcenter XD120f

If you do it from the feeder you can get a line, because the paper goes past a strip of glass. It could have white out on it or some dirt. Clean that glass.

I have the same problem and was told by the telephone helpdesk that the machine cannot copy double-sided to double-side. The duplexing referred to is copying 2 single-sided documents onto one single sheet on both sides....Like whoever does that! This is misleading on Xerox's part . Colin B.

Solutions for : Vertical Black Lines on Copies When the Automatic Document Feeder and Document Glass are Used Solution : Clean the Drum

1. Make sure there is paper loaded in the paper tray.
2. Press the [Menu / Exit] button on the Control Panel.
3. Press the [Up] or [Down] arrow button until 'Maintenance' is displayed on the Display Screen.
4. Press the [Enter] button. 'Clean Drum' will be displayed.
5. Press the [Enter] button. 'Cleaning Drum Please Wait' will be displayed and a sheet of paper will be printed. Toner (Dry Ink) particles on the Drum will be affixed to the paper.
6. Repeat steps 1 - 5 until the page prints without any Toner particles.

Clean the document feeder scanner glass. This is the much smaller strip of glass that is to the right of the large main glass. This strip of glass is used ONLY when using the feeder. So if you are getting a dark line when using the automatic feeder but not when laying a document on the glass then just clean the strip glass. 100% sure this is your problem. You may need to clean it several times as I have seen stuff get stuck to this glass.
Good Luck and Thank You for using Fixya.

If the problem only happens on copies or sent faxes then no it is not your drum. There is something on your scan glass. My guess is you are getting the line on your copies when you run the original through the document feeder. If you get lines through the document feeder but not on copies made off the glass then it is a dirty scan glass. There is a thin glass strip where the document feeder feeds the original. Usually something like white out that did not dry smears off an original and ends up on this thin strip of glass. Scratch it off with your finger nail and use some glass cleaner to resolve the problem. The scan glass is about 1/2 an inch to an inch wide and will be on the same side of the machine that the copier feeds the originals in on

The most common cause of blank (void) lines on a scanned document is from whiteout on the glass where the page is scanned when using the document feeder.
If there is a clear mylar sheet on the bottom of the document feeder, the whiteout may be there instead.

If there was dirt or a dark smudge on the glass (or mylar), it would show up as a black line, but whiteout is white, and shows up as a void (blank) line.

if using the feeder probably face up as it will likely pull the document in and invert it to lay face down on the scanning glass.

if you lift up the feeder (like lifting the top of a copy machine), then it would be face down on the glass.

there should be an image on the feeder illustrating how the document should be placed - if it looks like a page with lines on it with a bent corner then it is face up.

What you want to do is this. Turn the machine off, then go to the back of the machine and unplug the document feeder, There is a white connector with 2 thumb screws holding it in place. loosen the 2 thumb screws and unplug the plug. With the feeder unplugged turn the machine back on and let it come to ready. Once it comes to ready turn the machine back off, then plug the document feeder back on and turn the machine back on. That should re detect the document feeder and work fine. The M20 for some reason just forgets it has a feeder and you have to force the plug and play portion of the software to detect the machine not having a feeder then seeing that is has one. I don't know why, not even the newest versions of firmware for the machine resolves that issue. Odd,,,,,

Open the document feeder and clean the scanner glass

There is a thin strip of glass that you will see when you lift the top feeder. There is most likely white-out on it.

When you use the top feeder, it doesn't use the large glass, it only 'rolls' the original document over this small strip of glass.