phaser 740 streaks

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On my printouts there are streaks at the top of the page, above the margins. They are four thin lines in each color.
If I print a black and white page only a black line appears.
They are not on the image itself, but they are on the paperedge.
The Image unit is at 95 %, but the printer isn't being used for a long time.
Can anybody help me?

Thanks,
Piet