Ricoh FT5233 Service Manual page 42

12 February 1992
1.5 DRUM TEMPERATURE CONTROL
1.5.1 Overview
(V)
Drum
potential
Exposure lamp voltage
Under low temperature conditions drum sensitivity drops and drum residual
voltage increases. This is a characteristic of the drum and may cause dirty
backgrounds on copies.
To compensate for this, a drum thermistor is installed on the ID sensor board
to monitor the temperature around the drum.
When the main switch is turned on, the CPU checks the temperature through
the drum thermistor. If the temperature is 25°C or less, the CPU applies
appropriate corrections to the exposure lamp voltage (low temp. correction),
to the grid bias voltage (V
voltage (V data correction).
R
When the temperature goes over 25°C, the V
pattern detection are performed and the above corrections are canceled.
If the temperature is already over 25°C when the main switch is turned on, no
correction is applied.
(V)
Drum
potential
(V)
data correction), and to the development bias
R
2-13
PROCESS CONTROL
Light intensity
pattern detection and V
R L