Canon NP6218, FY8-13EX-000 service manual Controlling the Fluorescent Lamp Heater

CHAPTER 4 IMAGE FORMATION SYSTEM

■Input to the Reversal Amplifier Circuit (if the intensity increased gradually)

	Input from intensity
Voltage (V)	adjustment sensor

Lighter

Reference voltage

(4V)

Darker

Time (t)

Reference voltage

(4V)

"C" "D"

Figure 4-109

■Changes in the Duty Ratio of the FLON signal

OFF

ON

FLON signal 'C'

OFF

ON

FLON signal 'D'

Figure 4-110

6. Controlling the Fluorescent Lamp Heater

As the temperature around the scanner increases, the resistance of the fluorescent lamp thermistor (TH3) lowers, thereby lowering the voltage of the fluorescent lamp thermal signal (FLTH). Based on the voltage, the fluorescent lamp heater control circuit on the composite power supply PCB turns on and off the fluorescent lamp heater drive signal (FLTHON).

You can force the fluorescent heater off by turning off the scanning lamp (fluorescent lamp) heater switch (SW2) during the months in which the heater is not needed.

4-8 COPYRIGHT © 1997 CANON INC. CANON NP6218 REV. 0 MAY 1997 PRINTED IN JAPAN (IMPRIME AU JAPON)