Development Bias Circuit - Ricoh A151 Field Service Manual

DEVELOPMENT
10. DEVELOPMENT

10.1 DEVELOPMENT BIAS CIRCUIT

Bias Trig (PWM) [ 0→0/5]


The main board supplies +24 volts to the CC/Grid/Bias power pack at CN1-1.
When the key is pressed, the CPU starts sending the bias trigger pulses
to CN1-4. This energizes the development bias circuit within the
CC/Grid/Bias power pack, which applies a high negative voltage to the
development roller. The development bias is applied whenever the drum is
rotating.
The bias trigger pulse applied to CN1-4 is a pulse width modulated signal
(PWM signal). The width of the pulses controls the voltage level of the
development roller. As the width of the trigger pulses increase, the voltage to
the development roller also increases. The power pack is equipped with its
own feedback circuit to monitor the development bias voltage.
A202/A203
Power Pack -
CC/Grid/Bias
(P1)
A203D506.wmf
8-16
Charge Corona
Grid
Development
Bias
A203D505.wmf
SM