Ricoh A250 Service Manual page 297

2. This symptom is also related to the mono-component toner developing system used by the
A250.
There are two causes:
A. Image density is determined by the amount of charge that the toner holds. However, regardless
of whether the charge held by the toner is too low or too high, the resulting image density will
drop. If the charge is too low, the necessary static electricity and therefore the amount of toner
used will also be low, causing a lower image density. If the charge is too high, the developed
toner will neutralize the charged image on the OPC drum causing the static charge necessary
for development will be relatively low. This will cause the amount of toner used to be low,
resulting in lower image density.
The reason for the initial low image density is therefore not related to the dual-component
development system. Rather, it results from a low initial static charge on the toner due to the
use of a development system where the uncharged toner is directly supplied to the development
roller.
B. Generally, toner is initially supplied to the development roller starting with the smallest particles.
If the particles are relatively small, the image density will be relatively low not only because the
toner density is visibly low, but also because the amount of charge in the toner is higher. In the
A250, image density begins to increase after the smallest toner particles have been used up,
approximately 100 to 250 copies. This symptom is not limited to the A250, and is present in
machines of other companies that employ the same type of development system.
It has been proposed that in order to increase the image density (i.e. improve the initial performance
of the toner), the development roller should be run idle. However, since the toner is not being used
(as there are no copies being made), the same toner will remain on the roller as it turns, subjecting
the toner to stress (which will cause the image density to drop). Therefore, although the symptom
produces copies with slightly low image density, it is limited to the first 100 to 250 copies, after
which the image quality will improve.
A countermeasure will therefore not be applied to these symptoms. In addition, a test for image
density was performed using a new cartridge (AIO) followed by 10 days of no use. After testing, no
change in image density was observed.
SM 7-13
COPY QUALITY
A250