Measure the distance (in millimeters) between the original and the ghost (i.e., the top of the original A to the top of the ghost A). Then, use the repetitive defect chart (the Phaser 7400 is on the second page near the bottom), to determine which of the internals of the printer is causing the ghosting. The solution is going to depend on which part is causing the issue.
Oh, and knowing if the ghosting was on all four toners (CMYK) or just a single one would also be useful information.
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