The image is smudged only on black

Sounds like you need a new black drum. If the smudge looks the same each time, you may have something on the drum that can be cleaned off, such as adhesive from a label. If that's the case, you can sometimes get away with cleaning the drum with a soft cloth and rubbing alcohol if necessary. Alcohol will leave a void spot for few copies, but will eventually go away unless the drum is really old, then it may not.