Ricoh B121 Service Manual page 302

The four-toner density control modes are as follows.
Mode
Toner supply decision
Toner control process
Toner supply amount
Toner end detection
Mode
Toner supply decision
Toner control process
Toner supply amount
Toner end detection
Mode
Toner supply decision
Toner control process
Toner supply amount
Toner end detection
Mode
Toner supply decision
Toner control process
Toner supply amount
Toner end detection
B121 Series/B259 Series
Sensor control 1 (SP2-921, "0"): Normally use this setting only
Compare Vt with a reference voltage (Vts or Vref)
Toner is supplied to the development unit when Vt is higher than
the reference voltage (Vts or Vref). This mode keeps the Vref value
for use with the next toner density control.
Vts is used for the first toner density control after a new PCU has
been installed, until it has been corrected with the ID sensor output.
Vref is used after Vts has been corrected with the ID sensor output
voltage (corrected during the first toner density control for a new
PCU).
Varies
Performed
Sensor control 2 (SP2-921, "1"): For designer's use only; do not use
in the field
Compare Vt with a reference voltage (Vts)
This toner control process is the same as sensor control 1 mode.
However, the reference voltage used is always Vts.
Varies
Performed
Fixed control 1 (SP2-921, "2"): For designer's use only; do not use
in the field
Compare Vt with a reference voltage (Vts or Vref)
This toner control process is the same as sensor control 1 mode.
Fixed (SP2-925)
Performed
Fixed control 2 (SP2-921, "3"): Use temporarily if the TD sensor
needs to be replaced
None
Toner is supplied every printed page regardless of Vt.
Fixed (SP2-925)
Not performed
6-44
DEVELOPMENT
SM