I have a brother copier model dcp 7025 and am experiencing a vertical line on copies where the original is fed through the top feeder tray but the copies are fine when the original is placed directly onto the glass.How can I rectify the problem.

You need to clean the narrow glass strip on the left side of the machine when you open the cover. There is likely lint or something on this glass. This is where the auto document feeder pages are "imaged".

You need to clean the scanner glass. Also known as the strip glass. It is a 1 inch wide strip of glass that runs from the front to the back. Your documents pass over this glass when they are scanned. Some of the wax crayon probably smeared off onto the glass and now when you scan the scanner sees these marks as stationary and thus records them as solid lines. Just look into the scanner section where your documents are fed in or depending on model, some are just to the left of the large original glass.
Good Luck and thank you for using Fixya.

Does this happen when he orginals go thur the document feeder? How does the copy look if the orginal is placed on the glass. Vertical feed problem mite be dirty rollers or dirty clutch,

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Take a look at your drum. If there's a green tab on the exterior, move that all the way to the left. That should get rid of the black line.

clean your scan glass (thin strip of glass running from front to back, underneath document feeder) with a soft cloth and alcohol.

Try cleaning the rollers inside the scanner including the glass inside and out with a soft damped cloth. Look also for a piece of paper, staple wires, paper clips or pencil lead jammed inside the rollers or somewhere in the corner.
Also, look for a foreign object or substance on the cold cathode tube light and clean it. Try also cleaning the mirror.

Hello sir; When you feed originals in portrait, the paper tray have to set by portrait direction too.

Open the document feeder and clean the scanner glass

Open up the document feeder. You will probably find wite-out on the scanner glass.

If the problem only occurs when using the document feeder, the problem is not usually caused by the drum. When using the document feeder, try to notice where the scanner (the light assembly under your scan glass)stops just before the paper is being fed. Some multifunction machines have a small piece of glass that is separate from the large scan glass and the scanner assembly stays parked underneith it as the original is being fed over it. Most likely there is something on the glass where the scanner parks as originals are being fed thru the feeder. When putting your original on the large scan glass to copy, the mark on the glass will only show as a spot, but will show as a vertical line thru the whole copy when using the feeder.