Toshiba DP120F, Руководство по обслуживанию

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March 2000 © TOSHIBA TEC 7-33 DP120F/DP125F Circuit Description
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.
Signal Name Type Active Description Destination
PTCCK2 I - Inch-based Clock PTC GA
PTCCK1 I - Milli-based Clock PTC GA
PMCLK O - Polygon Motor Clock LSU
PMTON O H Polygon Motor Drive Signal LSU
PMTSTS I H Polygon Motor Synchronizing Signal PTC GA
LEN O H Laser Enable Signal LSU
LDATA O - Print Data EET
VDIN I - EET Print Data PTC GA
VDOUT O - LSU Exposure Data LSU
UFEO I - LSU Horizontal Synchronizing Signal LSU
MT2C0 O - LSU Sample/Hold Clock Signal IC262
LSUSH O L LSU Sample/Hold Signal LSU
Print density Pulse width of VDOUT signal Drum bias voltage (V)
+2 6/8 0
+1 6/8 -100
0 5/8 -100
-1 5/8 -200
-2 4/8 -200
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.