Panasonic KX-FLB852CX Service Manual page 255

7.15.2. CHG-BIAS (Charge BIAS)/GRID/ UNIT
When CHG REM becomes "L", IC604 turns ON the transistor Q614, and Charge BIAS (200µA) is output from CHG OUTPUT.
GRID BIAS is generated by the current flowing in the GRID circuit via charge wire and GRID.
7.15.3. DEV DC BIAS UNIT
When CHG REM is "L", 5.425kHz PWM (Pulse Width Modulation) is input from IC604 to DEV CLK through Q611, developing
voltage corresponding to the DUTY of PWM signal is output from DEV OUTPUT. Also DUTY is adjusted by the utilization of the
developing unit and environmental temperature.
7.15.4. DEV AC BIAS UNIT
When 17.5kHz rectangular wave signal is input from IC600 to DEV AC through transistor Q639, 325 Vp-p 17.5 kHz rectangular
wave of developing AC voltage is output from DEV OUTPUT. This voltage is overlapped with developing DC voltage and output
as AC voltage that includes the development DC voltage.
7.15.5. TRA (+) BIAS (Transfer (+) BIAS)/TRA (-) BIAS (Transfer (-) BIAS) UNIT
When CHG REM is "L" and TRA CLK is "open", Charge BIAS (200µA) is output from CHG OUTPUT, and at the same time
Transfer (+) BIAS (800V) is output from TRA OUTPUT. When 5.425kHz PWM (Pulse Width Modulation) signal is input to TRA
CLK through transistor Q609, Transfer (-) CURRENT BIAS corresponding to PWM signal is output from TRA OUTPUT.
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KX-FLB852CX / KX-FLB852CXS