RICOH FT2212
Service Manual

TONER SUPPLY

4 July 1996

6.3.3 Fixed Supply Mode If 4 is selected in SP30, the TD sensor is not used for toner supply control. A fixed amount of toner is supplied at every copy cycle. The toner supply amount is determined by the SP32 setting. 6.3.4 TD Sensor Check and Toner Supply Timing During every copy cycle, the TD sensor voltage is monitored for three seconds after the machine starts developing the image on the drum. The CPU checks the voltage every 40 ms and stores the second highest voltage of every 250 ms period. Then the stored voltages during the three seconds are averaged, and the average is used as the TD sensor value for the copy. The toner supply clutch on time for detect supply mode using TD sensor output depends on this value. If the machine determines that toner needs to be added, the toner supply clutch turns on just after the trailing edge of the copy paper passes the transfer corona unit. If the copy paper is shorter than A4/LT size, the clutch is energized for 3 seconds after the machine starts developing the latent image. 6.3.5 Abnormal Condition in Toner Density Detection If the calculated value of the TD sensor goes below 0.2 volts, the CPU determines that the toner density detection is abnormal. The CPU changes from the detect supply mode to the fixed supply mode. At the same time, either the Auto ID indicator or the selected manual ID level starts blinking, and the machine can be operated. Under this condition, the machine will not perform the toner end detection. If the value recovers above 0.2 volts, or the main switch is turned off and on, this condition is canceled and the toner density detection will recover to the previous settings.

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