Ricoh FT5540, Service Manual

Page: 78 / 734

31 August 1989
5.5 IMAGE DENSITY CONTROL
Image density is controlled in two ways: 1) by changing the strength of the bias voltage
applied to the development roller sleeve, and 2) by changing the strength of the voltage
applied to the exposure lamp.
Applying a bias voltage to the development sleeve reduces the potential between the
development roller and the drum, which reduces the amount of toner transferred; so, the
stronger the bias voltage, the lighter the copy image. Similarly, increasing the voltage to the
exposure lamp causes an increase in light intensity, which also results in lighter copies.
The control method is different depending on whether the image density is selected manually
or the automatic ID system is used.
Manual Image Density Control
DARK < - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - > LIGHT
ID Level 1
2 3 4 5 6 7
V1: Bias 260
260 260 290 290 320 350
V2: Lamp Vo-5 Vo-3.5 Vo-1 Vo Vo+2.5 Vo+3.5
Vo+4.5
Voltage
Vo = 50 to 80 volts ac
When image density is set manually, the development bias (base level) and the exposure lamp
voltage vary as shown in the above table. The lamp voltage at ID level 4 (Vo) can be adjusted
with SP mode #48.
2-30
NOTE: In Auto ID mode, the lamp voltage remains at Vo (no compensation is applied).