HP Color LaserJet CM4730 Service Manual - Page 184

The DC controller divides the oscillation frequency of the oscillator (X1201) and generates the reference clock signal. It compares the intervals between the reference clock signal and the BD input signal (/BD1I) with the frequency comparator, and monitors the rotational count of the scanner motor. The DC controller controls rotational speed by sending an acceleration signal (/SCNACC1) or deceleration signal (/SCNDEC1) to the scanner motor driver based on the detected rotational speed. Figure 4-15 Scanner motor circuit diagram on page 164 illustrates the scanner motor control system. Figure 4-15 Scanner motor circuit diagram The scanner motor control circuit manages the following control and detection functions: ● Speed control. Maintains the rotational speed of the scanner motor at a constant speed. ● Phase control. Prevents color misregistration by eliminating rotational variations in each color's scanner motor and adjusts the phase of the scanner motor. ● Failure detection. Monitors the frequency comparator in the ASIC and determines whether the scanner motor is rotating at its specified rotational count. 164 Chapter 4 Theory of operation ENWW