Canon NP2120 Service Manual page 70

E. Controlling the Development
Bias
1. Outline
Figure 3-28 shows the circuit that controls the
development bias and has the following functions:
and OFF.
The copier varies the voltage level of the develop-
mentbiastocontrolthecopydensityaccordingtothe
settings of the following:
When the black developing assembly is set. J24-1
and -4 are shorted by means of a jumper wire,
thereby identifying the presente of the assembly.
2. Mechanism
a. Tuming the Development Bias AC Component
The square wave osciilatorcircuit is at work at all
times as long as power is present.
The above condition deprives the developing
cylinder of AC biases.
The above condition causes the AC bias switch
circuit to go OFF; as such, the output of the
square wave oscillator is sent to the Tl drive
circuit. raised lo 1300 VAC, and is supplied lo the
developing cylinder. The output of the AC high-
fied by the rectifier circuit and supplied to the
static eliminator (about 3.2 KV).
C A N O N NP2lZO/ZGZO RN.0 MAY 1990 PNINTED I N J A R N I M P R I M E AU JAPONI