Canon PC980 Service Manual - Page 61

CHAPTER 3 EXPOSURE SYSTEM b. Controlling the Intensity of the Scanning Lamp The intensity of the lamp is controlled by the scanning lamp active voltage signal sent by the DC controller PCB in serial. The microprocessor (Q900) on the composite power supply PCB sends the intensity adjust- ment signal (PWM_1KHz) in response to the scanning lamp active voltage signal. In turn, the phase control circuit (HIC 001) controls the voltage supplied to the scanning lamp. The PWM_1KHz signal varies according to the setting of VR107 mounted on the DC controller PCB between 10% and 90% in terms of pulse duty ratio or between 50.5 and 80 V for the 120 V model (between 85.7 and 145.8 V for the 220/240 V model) in terms of actual voltage by way of phase control. However, the intensity remains a specific value for AE exposure so that it is 56 V for the 120 V model (108.5 V for the 220/240 V model) in terms of actual voltage. t [msec] ON OFF 1 [msec] 1kHz 1 Pulse duty= t/ 1k × 100 [%] Figure 3-202 c. Monitoring the Activation of the Scanning Lamp The activation detection signal (LAMP_DETECT) is sent to the microprocessor (Q900) on the composite power supply PCB as long as the scanning lamp remains on. The composite power supply PCB sends the lamp activation signal to the DC controller PCB in serial by way of monitoring the activation of the scanning lamp (LA1). Related Error Code E220 • The lamp activation detection signal is not detected for 1 sec or more although the scan- ning lamp activation signal has been sent. • The lamp activation detection signal has been detected for 1 sec or more although the scanning lamp activation signal is not sent. If an error has been detected, the power switch will be turned off after indicating an error code for 2 sec. COPYRIGHT © 1999 CANON INC. CANON PC800s/900s REV.0 AUG. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON) 3-11