Toshiba DP120F Service Manual page 342

The PTC GA converts the received VDIN signal to VDOUT, outputs it with the timing of the
UFEO signal for setting a reference for the printing position in the scanning direction, and
drives the LSU.
The print density on recording paper is determined according to the pulse width of the VDOUT
signal and the drum bias voltage output from the HVPS. (For controlling the drum bias voltage,
refer to "8. HVPS" in this chapter.) The relations between the print density, VDOUT signal, and
drum bias voltage, are shown in the table below.
Print density
+2
+1
0
-1
-2
Since the power of the semiconductor laser fluctuates significantly due to a temperature change,
the LSU contains a power monitoring photodiode. The LSUSH signal to be generated based
on the MT2C0 signal output from the PTC GA controls the current value of the laser so that the
photodiode current will be uniform.
Sample (LSUSH signal = LOW) means:
A laser beam is applied from the moment when the laser scanning position is off the drum to the
moment when the start sensor detects the next side of the polygon during which power control
is performed to obtain the proper current value.
Hold (LSUSH signal = HIGH) means:
The power is not monitored while a latent image is provided on the drum for the print area, but
a laser beam is applied at the current value found during sampling.
Signal Name Type
PTCCK2 I
PTCCK1 I
PMCLK O
PMTON O
PMTSTS I
LEN O
LDATA O
VDIN I
VDOUT O
UFEO I
MT2C0 O
LSUSH O
March 2000 © TOSHIBA TEC
Pulse width of VDOUT signal
6/8
6/8
5/8
5/8
4/8
Active
- Inch-based Clock
- Milli-based Clock
- Polygon Motor Clock
H Polygon Motor Drive Signal
H Polygon Motor Synchronizing Signal
H Laser Enable Signal
- Print Data
- EET Print Data
- LSU Exposure Data
- LSU Horizontal Synchronizing Signal
- LSU Sample/Hold Clock Signal
L LSU Sample/Hold Signal
Drum bias voltage (V)
Description
7-33
0
-100
-100
-200
-200
Destination
PTC GA
PTC GA
LSU
LSU
PTC GA
LSU
EET
PTC GA
LSU
LSU
IC262
LSU
DP120F/DP125F Circuit Description