Exposure Lamp Control Circuit - Toshiba DP1600 Service Manual

7.5.2 Exposure Lamp Control Circuit

This circuit is made up of the motor control IC (IC4), and the transformer, capacitor and other peripheral
elements on the Inverter PWA and controls the lighting of the exposure lamp.
The circuit configurations are different on the DP1600 series and DP2000/2500 series.
DP1600 series
The motor control IC (IC4) turns the LAMP signal to the HIGH level.
The transistor (Q3) turns on and the LAMP signal turns to the GND level.
The transistor (Q3) on the Inverter PWA turns on to apply +24V to the Inverter PWA.
The transistors (Q1, Q2) are biased by the starting resistors (R1, R2). At this time, either of Q1
and Q2 turns on due to the transistor characteristics.
The following explains a case where Q1 has turned on.
If Q2 has turned on, Q1 and Q2 should be substituted for each other.
Bias voltage of Q1 is produced in the Nb winding of the transformer (T1) to allow Q1 to completely
turn on. At this time, Q2 turns off because it is reverse biased.
When current flows through T1, the primary circuit resonates due to the Np winding and capacitor
(C1). This causes the bias voltage of the Nb winding to be reversed.
Q1 turns off due to the reverse bias voltage and Q2 turns on.
As Q1 and Q2 turn on and off alternately in this way, high-frequency voltage is produced in the
primary circuit of T1. This voltage is boosted by the Np winding and Ns winding and supplied to
the exposure lamp for lighting.
Scanner control PWA
CPUA0~19
IC4
IC1
Motor
Scanner MPU
CPUD0~15 control IC
1600/2000/2500 SCANNER
Inverter PWA
ICP1
+24V
1 1
2 2
58 LAMP
Q3
3 3
PG PG
7 - 10
Q3
T1
Q1
Np
R1
C1
R2
Ns
Q2
Nb
1
Exposure lamp
4
08-05-01
December 2000 © TOSHIBA TEC