Gradation Correction Control - Konica Minolta 7155 Service Manual

DEVELOPING UNIT

[6] Gradation Correction Control

Gradation correction control is performed by
TCSB (toner control sensor board), M2 (drum),
M3 (developing), and so on under the control of
PRCB (printer control board).
1. Operation
The gradation characteristics of the toner density
versus exposure amount at the image forming
section (drum area) are detected to obtain a lin-
ear relation between the image density on a doc-
ument and the copying image density.
(1) Method
Exposure is performed with the laser PWM var-
ied in several steps, and development is per-
formed at the sleeve speed obtained by Dmax
correction.
Next, each density is read by the
on TCSB (toner control sensor board) to detect
the gradation characteristics of image density.
The gradation characteristics obtained here are
used as the values for correcting the laser expo-
sure amount.
Gradation correction control must be performed
in two ways: 1-dot PWM (for normal mode) and
2-dot PWM (for photo mode).
12V
A.GND
G SIG EX
LED CONT
TNLED REF
TCSB
DEVM CW/CCW
PRCB
DCPS
γ
sensor (PD2)
2-G-6
5V
P.GND
DRUM CONT
DRUM CLK
CW/CCW
DRUM EM
5V
P.GND
DEVM CONT
DEVM CLK
DEVM GAIN
DEVM EM
12V2
S.GND
MS1 MS2
24V2
P.GND
(2) Timing
a) When the fixing temperature is lower than
°
122 F at SW2 (sub power) ON
b) Every 5,000 prints, upon competion of the
last job.
2. Signals
a. Input signals
(1) G_SIG_EX (TCSB to PRCB)
This signal monitors the output voltage from the
γ
sensor (PD2) on the TCSB (toner control sen-
sor board) as well as the light reflected by the
drum surface (without toner).
The voltage applied to the gradation detection
LED is corrected by TNLED_REF so that the out-
put voltage becomes 3.0 V (calibration).
Reference voltage: 3.0 V
<Timing>
Before gradation correction.
b. Output signal
γ
(1) LED CONT (PRCB to TCSB)
Gradation detection LED ON/OFF control signal
[L]: LED ON
[H]: LED OFF
M2
M3