Canon FY8-13EX-000, NP6218 service manual Controlling the Intensity of the Scanning Lamp FL1

CHAPTER 4 IMAGE FORMATION SYSTEM

■Scanning Lamp ON Pre-Heating Control (during copying operation I)

FLON signal

FLPRHT signal

1KHz

40% or more

OFFOFF

ON

5KHz

44.4%

ON

5V

0V

Figure 4-108

5. Controlling the Intensity of the Scanning Lamp (FL1)

•If the intensity of the fluorescent lamp is too low at power-on,

The starting power of the intensity adjustment sensor lowers, and the fluorescent lamp intensity adjustment signal (FLS) of the amplifier circuit on the DC controller increases. In response to the signal, the microprocessor (Q512) on the composite power supply PCB reduces the duty ratio, thereby increasing the ON time of the FLON signal.

The current flows through the filament of the fluorescent lamp when both the MPWM signal (150 kHz) and the FLON signal (1 kHz) are on.

•If the intensity of the fluorescent lamp is too high at power-on,

The starting power of the intensity adjustment sensor rises, and the fluorescent lamp intensity adjustment signal (FLS) of the amplifier circuit on the DC controller PCB decreases. In response to the signal, the microprocessor (Q512) on the composite PCB increases the duty ratio, thereby decreasing the ON time of the FLON signal.

Caution:

Gain Adjustment for the Intensity Adjustment Sensor (VR301)

If you replaced the intensity adjustment sensor or the scanning lamp (fluorescent

lamp, FL1), or the DC controller PCB, you must always perform gain adjustment for the intensity adjustment sensor using VR301 on the DC controller PCB. (See the p. 10-10.)

COPYRIGHT © 1997 CANON INC. CANON NP6218 REV. 0 MAY 1997 PRINTED IN JAPAN (IMPRIME AU JAPON) 4-7