Xerox phaser 6010 - black spots on sheet

Good evening, I bought this printer, but it is used, when I print on the sheet all pieces of toner are released.
The flaw was reduced when I started some blank page printouts with no text.
But it recurs every 3 or 4 printed pages.
Which component is causing this problem? the fuser or the cleaning blade?
If disassembly the printer and clean the black fuser roller? solve?

 

Either it’s burnt toner coming off the fuser, or the black developer station is leaking all over the place.

take a peak at the fuser roller. See if there’s any toner gummed up on the roller.

Then check the general paper path and image transfer belt. Is there black power all over the place? If so, then the black imaging station is the culprit

 

yes I can see burnt toner on upper fuser roller (the black roller but the orange is clean), the transfer belt is clean.
but after the print of this page the defect is more reduced, now I print many blank sheets and see if solve.
This defect is caused also from bad quality toner, that don't keep on sheet?

 

Could be caused by a few things. The most common reason I’ve seen is when a substrate is ran with improper settings. Particularly a light media being ran with settings for heavy media. The fuser has far more heat than it needs, and instead of fusing the toner to the sheet, the hot rollers pick up the toner. It causes a goopy mess that’s hard to get rid of.

it could also happen if the fuser is well past it’s life and needs maintenance or replacement.

 

I don't think is fuser, the printer have only 6000 copies, probably the previous owner have used bad quality toner that don't fixed on the paper and caused this issue.
As I said, now this happens occasionally, after printing the sheet with the pink print
I have checked the black fuser roller and it seems to me that most of the burnt toner has been removed, if it continues I disassemble the printer and clean it with isopropyl alcohol.
I don't want to do more than this because I risk doing some damage, I'm not a technician.

 

I replaced the two toner cartridge Black and Magenta and increased fuser temperature in "Xerox printer Utility" .
After the print of many sheets the problem appear solved, as I said in prevoius post the burned toner on fuser roller has been removed gradually.

thanks to all for help.