Ricoh G148, Service Manual

Page: 471 / 537

• SP2507-002 (ID Sensor Interval – Page Setting) is available for customers who are con-
cerned about changes in toner density during long copy jobs and may want to specify an
interval to force creating and reading the ID sensor pattern. However, enabling this SP will
pause copying for 2 or 3 seconds every time the ID sensor pattern is created and read
2. The CPU uses the Vsp/Vsg readings to calculate a new value for Vref (TD sensor reference voltage).
3. Finally, Vt and Vref are compared. If Vt is higher than Vref, the CPU switches on the toner supply clutch
to supply more toner to the development unit.
Pixel Count Toner Supply Mode
This mode should only be used as a temporary countermeasure while waiting for replacement parts, such
as a TD sensor.
For each copy, the CPU adds up the image data value of each pixel and converts the sum to a value
between 0 and 255 (0 = blank page, 255= black page).
The toner supply clutch on time is calculated using the same formula, but the GAIN value is fixed at 0.7.
TD Sensor Initialization
The TD sensor must be initialized with SP2801 (TD Sensor Initial Setting) at the following times:
• The first time the development unit is filled with developer
• Every time the developer is replaced.
The sensor control voltage is adjusted until the output is 3.0
±
0.1V. Then, after setting the control voltage,
Vt is sampled 100 times, these samplings are averaged, then the average is used to set the standard value
for Vt.
• After developer is replaced, you must execute SP2801.
• After the TD sensor is replaced, you must execute SP2801.
• After a partially used development unit from another machine is installed, you must use SP2220 (Vref
Manual Setting) to enter the Vref value for that unit, and use SP2906-001 (TD Sensor Control Voltage
Setting) to enter the TD sensor control voltage.
• These initial values are stored in NVRAM. Before replacing the NVRAM, print an SMC report so you
can re-enter these settings manually after the NVRAM is replaced.
Determining Vref
At certain intervals (see ‘Sensor Control Mode, step 4), the ID sensor reads the bare drum and the ID sensor
pattern on the drum.
Vref is calculated from Vsp and Vsg as explained in the Process Control section of the manual.
6. Details
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