"Alasdair Campbell" wrote in
.uk:

LaserJet 4050N with blank line lengthways down middle of each print,
about 5mm wide. Only appeared after being unused for 3 months.

Service manual says I need to start replacing huge parts of the
printer, but I was hoping for other ideas.
I've dismantled it as far as I can and can't see any alien objects, or
signs of wear.

Haven't started looking at main printing stage, as I wouldn't know
where to start. Are there manuals that doc dismantling this sort of
thing?



Take a look at:

http://www.feedroller.com/Store/hp2.php

and the support forum at

http://www.fixyourownprinter.com/