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Drum Motor Control Circuit
The drum motor drives the photographic drum that is central in the printing cycle and
the pre–drum roller that controls the transfer speed of cut–sheet. Therefore, stable
rotation is required of the motor. A rotary encoder is set on the rotating axis. The
output pulses and standard pulses (equivalent to 878.90625 rpm motor rotation)
created by a crystal oscillator via a frequency divider circuit are compared in a PLL
(phase locked loop) circuit, and the input voltage to the motor is controlled to where
the difference between the two are minimal. (The PLL circuit uses a special IC.)
Further, there is a drum counter encoder on the drum proper axis (inside rear panel).
This is set to where the drum counter counts up by input pulses from this encoder (1
pulse per 1 rotation) when the count enable (Count EN) signal is valid, by the
following circuit.
330
470
+24V
2SC 2/20
Electrical and Wire Data
6–41
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