Black mark on printed copies

If the smudge marks are down the edges of the paper, the PC Kit needs replaced.

try to stop the sheet just before it enters the fuser and see if the marks are on the paper already. if not then it has to be the fuser if they are them you have another issue.

replace the black image unit and the fuser

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It could be leaking toner from the recovery area that sis on top of the dum, it removes any toner that was not transfered to the paper. You would have to remove it and empty out the toner.

Transfer belt cleaning unit. The transfer unit is above the drums and the cleaner is on the left side. Remove it and I would bet you see a similar band as what your seeing on your prints. You can try wiping of the cleaning blade in the unit or you may have to replace it.

Are you using third party ink? make sure your ink is xerox OEM. This will clogg up the inkjets and ruin the print head for ever, If you have always used the third party ink then you might want to get a new print head. . If you have used xerox ink then It sounds like the magenta reservoir has spilled over the cyan. This is caused by moving the printer and not waiting for the cool down procedure. Also you might want to change the print head wiper. If the print head wiper is over used it won't clean the print head properly and what that causes is for ink to build up and causes smudge. also make sure the drum maintance kit is still in good shape. (its the yellow roller on the right side of the printer. Well hopefully this helps .

I also had this issue, waste tone was comming from the transfer belt, had a good clean out been good for months now.

Hello sir;The streak line from printing also should be from copy, because the line come from imaging unit, check the meter count if close to or over 50,000 then replace drum and drum blade, it will take care the problem.
The brother printer you need to replace imaging unit( drum unit).

please check the pc drum, if there is also a mark in same location, then you have to replace pc drum, if not, take a look at transfer belt, same options, if TBU is also clean, then see fusin unit rollers.

Ramana is the black stripe just showing up on copies or faxes or does the stripe occur when you are printing from your computer. If the stripe only occurs when copying or faxing then more than likely the scanner glass is dirty. White out liquid on the scanner glass is a common.If it happens when printing fromyour pc, the problem will be in the toner cartridge or the fusing assembly.
Change the cartridge first to see if it goes away. Check the scanner glass, especially the small glass strip on the left side of the scanner or the right side where you place the original paper. These areas should be completely clear and clean of any scratches or smudges.
Last is the fusing assembly. If you tried everything else and theline continues to bother you, the fusing assembly sleve is probably torn. This would have to be replaced. The part number is RM1-0865-040CN.