I changed the toner and drum in my printer/fax, and cleaned the little glass window, but still get a line thro

I changed the toner and drum in my printer/fax, and cleaned the little glass window


I still get a line through my documents, what is left?I changed the toner and drum in my printer/fax, and cleaned the little glass window, but still get a line thro
what sort of printer is it, does it have a fuser unit because this is a common fault ,if a fuser unit is gone that it leaves a line down the page