Ricoh FT8680 Service Manual page 32

PROCESS CONTROL
1.3.5 Charge Corona Current Adjustment
The charge corona current is measured and adjusted automatically by the
drum current detect PCB.
The charge corona current flows to the drum current detect PCB through the
drum and the drum shaft. The drum shaft is grounded by the drum current
detect PCB usually. However, during the process control data initialization,
the main PCB activates the corona current circuit in the drum current
detection PCB which converts the drum current to a voltage and separates it
into ac and dc component outputs. Then, the main PCB reads them through
A/D converters as digital data. The main PCB adjusts the corona current by
controlling the PWM signal to the charge corona power pack.
When the auto drum current adjustment mode is selected by the SP mode,
the drum current detect PCB is used to measure and adjust other corona
outputs in the same way.
Drum Current Detect PCB
2-8
31 July 1995
Potential S.
Id Set
MainPCB
A11D502.wmf