Ricoh Aficio MP 2550B, Service Manual

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Development
D017/D018/D019/D020 6-44 SM
Mode Sensor control 3 (SP921, "4". DFU
Toner supply amount Varies
Toner end detection Performed.
Toner Density Sensor Initial Setting
The TD sensor initial setting procedure is done by SP2801. During TD sensor initial setting,
the TD sensor is set so that the TD sensor output to the value of SP2-926 (default: 2.5V).
This value will be used as the standard reference voltage (Vts) of the TD sensor.
Toner Density Measurement
Toner density in the developer is detected once every copy cycle. The sensor output
voltage (Vt) during the detection cycle is compared with the standard reference voltage
(Vts) or the toner supply reference voltage (Vref).
Vsp/Vsg Detection
The ID sensor detects the following voltages.
ƒ Vsg: The ID sensor output when checking the drum surface
ƒ Vsp: The ID sensor output when checking the ID sensor pattern
In this way, the reflectivity of both the drum surface and the pattern on the drum are
checked. This compensates for any variations in the reflectivity of the pattern on the drum
or the reflectivity of the drum surface.
The ID sensor pattern is made on the drum by the charge roller and laser diode.
Vsp/Vsg is not detected every page or job; it is detected at the following times to decide
Vref:
ƒ When the machine is turned on or returns from the energy save mode and the hot
roller temperature is less than 30 °C. The temperature threshold can be adjusted with
SP2995 001
ƒ After the total number of prints exceeds 300 pages. If this total is exceeded during a
job, the pattern is created at the completion of the job. This total can be changed with
SP2995 002.
ƒ SP 2995 003 determines whether the job is interrupted to make the ID sensor pattern.
If it is set to 1, the job will be interrupted.
Toner Supply Reference Voltage (Vref) Determination
The toner supply reference voltage (Vref) is the threshold voltage for the toner supply
determination. Vref is determined using the following data: