Toshiba TLP411E, Technical Training Manual

Page: 82 / 84

9-3
CM04 is a capacitor to stabilize the fluorescent lamp dis-
charging current. After the discharging starts, CM04 lim-
its the flow of the current with the reactance of CM04
(XC = 1/
w
c).
Before the fluorescent lamp turns on, the collector pulse
of QM03 is 70 – 80 V(p-p). The voltage is stepped up to
420 – 480 V(p-p) by LM03 and applied to the fluorescent
lamp. When a filament is warmed, the discharging starts
and the collector voltage of QM03 becomes approx. 30
V(p-p). The fluorescent tube voltage at turning on is
approx. 120 V(p-p).
SM01 works as a ON/OFF switch for the camera power
supply. When pin 10 of SM01 develops “L”, the power is
supplied to the camera.
The waveforms of each section at operation is shown in
Figs. 9-3 and 9-4.
Fig. 9-3
Fig. 9-4
+30V
– 80V
0V
– 0.22A
+0.16A
0
70 kHz
Fluorescent
lamp
voltage
Fluorescent
current
2. TROUBLESHOOTING
2-1. Fluorescent does not turn on
OK
OK
NO
NG
YES
NO
YES
Replace
fluorescent lamp.
12V : between pins
13 and 8 of PM01.
Drive PC board, Z500
QM02 base.
Pulse more than
25 V(p-p) is output at
QM03 collector.
More than 10V.
Fluorescent
switch.
(SC302)
Less than 3V.
Check secondary
side of LM03.
Not cut
Cut
Check power
supply unit.
Replace
QM03 and RM04.
Replace Z500.
Repair inverter
PC board.
31V
0
0
1.5A
70 kHz
QM03
Collector
voltage
Collector
current