Epson AcuLaser C1900 Reference Manual page 292

You may not be using the
correct type of paper for your
printer.
There may be a problem with
the photoconductor unit.
292
Troubleshooting
EPSON special paper or smooth,
high-quality copier paper is
recommended for best results. See
"Available Paper" on page 29 for
information on choosing paper.
Replace the photoconductor unit. See
"Photoconductor Unit" on page 246.