Blotches my Xerox Workcentre M15 has started putting black blotches at intervals along one edge of each page, whether printing or copying.

This is due to excessive wear on the transfer belt or a depleted transfer belt cleaner.. How many copies have been made since they were replaced. Xerox WorkCentre 7845 Transfer Belt Cleaner Genuine M5313

Hi Cnorini ,
Check this video and solve your problem.
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There is a problem with the Laser Unit
need to replace the LASER nit or need to open and clean the unit will solve the issue

read this.
http://www.printertechs.com/tech/print-defects/blackpages.php

If your on maintenance tell them you want a replacement. If you have a maintenance agreement you are entitled to an identical replacement. Write a letter, with the serial number, peoblem and tellt them you want to exercise your TSG agreement. Total Satisfaction Agreement.
Not fixing it is rediculas.

I would go to the xerox website and try downloading the PCL5e driver. It works just as well and even better in most cases. I hope this helps.

Hello sir; Just replace drum cartridge, it will take care your problem. GOOD LUCK!

Its your drum or fuser rollers

I'm sorry to tell you, this is likely a drum issue.

You probably need to have a certified engineer examine the machine.

Have you tried speaking with the local service center to see if they have experienced similar issues? It might be free information.

Erik.

What driver did you download? The PS driver is much less capable and I am wondering if thats what you downloaded.
I am using the PCL driver and the selections are 1 sided, 2 sided long edge , 2 sided short edge.
Unless you are runnung CAD, you really should be running a PCL driver.
Maybe I am misunderstand what you are telling me also.
If you have the PCL driver and thats still a problem let me know and I will forward all I can find.