Ricoh FW780 Service Manual - Page 59

5.5 T/S CORONA CIRCUIT Rev. 5/95 The T/S power pack is powered by +24 volts (Va) from the PSU. The dc/dc converters and dc/ac inverter change the +24 volts supply into the high voltages used by the transfer and separation coronas. The main board turns on the transfer corona using PWM signal (T.Drive). This turns on the dc/dc converter, which applies a high voltage of approximately --5.0 kV to the transfer corona wire. The main board turns on the separation corona using PWM signals (S.AC Drive and S.DC Drive). The dc/dc converter and dc/ac inverter circuits then apply approximately 5.0 kV ac and --200 V dc to the separation corona wires. A larger transfer current is applied when the fusing unit is in high or low temperature mode than in normal temperature mode. In high or low mode, thin copying paper (translucent paper or film) may be wrapped around the drum. This may cause the paper to be jammed or transported incorrectly. To correct for this, the separation current is increased in high and low modes. To ensure good copy quality in high mode, the PTL (pre-transfer lamp) is off during the copy process. A larger separation current is applied at the leading edge of the paper to improve the separation in high temperature mode. When roll feeder is installed, a larger transfer current is applied at the trailing edge of the paper to improve transfer at the curled trailing. A163 2-23 SM