Canon 1023if light area length of copy

[SAR]

Customer bought a new drum which didn't fix the issue. Dev unit mag roller looks fine, I ran a piece of paper in the mag roller gaps to clean it out. Is there a laser glass that can be cleaned somewhere? Removed the drum and looked everywhere ,but didn't see it.
Apologies for the lack of knowledge, but have never worked on one of these before.
Thanks!

[Brian8506]

The laser is above the drum. The drum has a tab on it that opens the laser shutter. To get you the laser you will have to take some covers off but it is above the drum. You may have some Toner building up in the there or dust.