Toner Density Control - Ricoh FT5540 Service Manual

6.4 TONER DENSITY CONTROL

The image density sensor checks the density of the sensor pattern image once every 10 copy
cycles. The CPU receives two voltage values directly from the sensor: the value for the bare
drum (Vsg) and the value for the sensor pattern image (Vsp). These two values are then
compared to determine whether or not more toner should be added.
2. Vsp > 1/8 of Vsg . . . . . . . . Low image density (toner is added)
When the image density is too low (Vsp > 1.5 volts), the CPU changes from the detect mode
to fixed toner supply mode. It will be recovered when VSP becomes less than 1.5 volts
automatically. If Vsg becomes less than 2.5 volts, the CPU determines that the sensed data is
abnormal, then it stops any further toner supply to the development tank. However, toner
supply is re-established if Vsg becomes greater than 2.5 volts. In either case the service call
indicator will blink.
SP mode #54 turns on the LED sensor manually. VR1 on the ID sensor board adjusts the
intensity of the sensor LED (the voltage of Vsg).
SP mode #55 displays Vsp and Vsg voltage values.
High image density (no toner added)
2-41
31 August 1989