MX-6240N, MX-7040N (serv.man32). Section 13 Operational Descriptions - Updated November 2012 - Sharp Copying Equipment Service Manual (repair manual). Page 37

MX-7040N  OPERATIONAL DESCRIPTIONS  13 – 37

Purpose: To maintain the sensitivity of the light receiving elements
even if the environmental conditions (temperature and humidity)
vary.

Execution timing: This adjustment is executed in the process con-
trol when the temperature or the humidity varies.

Method: Use the patch written on the primary transfer to adjust the
sensor sensitivity.

Purpose: To maintain the light emitting quantity of the sensor even
if the sensor LED is aged or the environmental conditions vary.

Execution timing: Every time when the process control is made.

Method: Reflection on the surface of the primary transfer belt is
used to adjust the sensor sensitivity.

1)

When the machine enters the high density process control mode, the secondary transfer unit remains in the printing position.

2)

While changing the DV bias voltage step by step, a number of toner patches in different densities are generated on the primary transfer
belt.

Front: The C toner patch is generated.

Center: The Bk, M toner patch is generated.

Rear: The Y toner patch is generated.

3)

Each toner patch density is detected by the image density sensor, and the DV bias correction voltage is calculated in the PCU PWB so that
the proper density is obtained from the relation between the DV bias voltage at the time when each toner patch is made and the toner
patch density.