Followed the direction step by step ...............problem solved!!!!!



Thank you very much for helping.
Now the copier is back alive, but the printing quality is still not so good. I suspect the mirrors and lense are still dirty somewhere. There are some repeatable black spots on same (or close to same) location on the paper. To me, it seems like coming from some dust in the optical path.
Any advice or trick for cleaning the mirrors and lense? Thanks.

