Turning On And Off The Scanning Lamp; Detecting The Activation Of The Scanning Lamp; Protection Mechanism - Canon NP6330 Service Manual

CHAPTER 4 IMAGE FORMATION SYSTEM

2. Turning On and Off the Scanning Lamp

The microprocessor on the DC controller PCB turns on the transistor (Q147) to send
the lamp ON command (LMPON) to the lamp regulator.
When the DC controller generates the light intensity signal (LINT), voltage of about
135 to 140 V (220 / 240 V) / 80 to 95 V (120 V) is supplied to the lamp, thereby turning
on the scanning lamp.
Reference:
If the density of copies has become excessively low because of deterioration in the
sensitivity of the drum, you may make correction by adjusting the setting of '301' in
service mode or 'U21' in user mode. (However, the setting in user mode 'U21' is
narrower than that of the service mode the range of the adjustment.)
A lower setting will increase the value of the LINT signal (analog) and, as a result,
will raise the supply voltage to the lamp, thereby increasing its intensity.

3. Detecting the Activation of the Scanning Lamp

The lamp regulator sends the lamp ON detection signal (LDT) to the DC controller
while the scanning lamp is on.
If the LDT signal remains on for 22 sec, the DC controller will identify the condition
as an error and, as a result, will generate the power switch OFF signal (PWOFF*) to turn
off the power switch and cut off the AC power supply.

4. Protection Mechanism

The machine is equipped with a thermal fuse to prevent malfunction of the scanning
lamp.
The thermal fuse (FU1) will melt in response to overheating (about 104°C / 219F or
more) because of a short circuit or the like around the scanning lamp, thereby cutting the
power supplied to the scanning lamp.
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COPYRIGHT © 1997 CANON INC. CANON NP6330 REV.0 MAY 1997 PRINTED IN JAPAN (IMPRIME AU JAPON)