NEC DPro2070SB, Service Manual

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1.4.4.1 Corner purity circuit operation
<TL: Upper left corner>
Pin 50 (PWM_DAC) of IC102 controls the TL in the range of 0 to 5V while regarding 2.5V as the reference
voltage, and the DC current of the above value will flow from pin 2 of IC803 to the upper left corner purity
coil.
<TR: Upper right corner>
Pin 49 (PWM_DAC) of IC102 controls the TR in the range of 0 to 5V while regarding 2.5V as the reference
voltage, and the DC current of the above value will flow from pin 8 of IC803 to the upper right corner purity
coil.
<BL: Lower left corner>
Pin 52 (PWM_DAC) of IC102 controls the BL in the range of 0 to 5V while regarding 2.5V as the reference
voltage, and the DC current of the above value will flow from pin 2 of IC801 to the lower left corner purity
coil.
<BR: Lower right corner>
Pin 51 (PWM_DAC) of IC102 controls the BR in the range of 0 to 5V while regarding 2.5V as the
reference voltage, and the DC current of the above value will flow from pin 8 of IC801 to the lower right
corner purity coil.
1.4.5 Vertical magnetic field landing cancel circuit
The vertical magnetic field landing cancel circuit is the circuit to compensate for the color shade and
deviation that reaches its maximum at the center in the horizontal axis direction and its minimum at the
upper and lower ends on the monitor surface, and the adjustment is done by DC current according to the
value displayed on OSM flowing to the speed modulating coil installed in the neck part of CRT.
It is controlled with 0 to 5V of 2.5V reference by IC102 pin 46 (PWM-DAC), and DC current of +/-150mA
(max) is made to flow to the speed modulating coil by IC804 pin 8.
1.4.6 Digital dynamic convergence clear (DDCC) circuit
In the digital dynamic convergence clear (hereafter called DDCC) circuit, the convergence compensating
current waveform is produced and amplified, and the convergence is compensated by the compensation
current flowing to the sub yoke that is installed as the rear unit of the deflection yoke.
Though the principle of the convergence compensation with the sub yoke is same as the CP ring, the CP
ring is used for the static variation with the parallel movement in the whole picture in the uniform magnetic
field with the permanent magnet but the sub yoke is used for dynamic variation that compensates a
desired position on the picture by controlling the current waveform that flows to the coil of the electric
magnet. (See Fig. 7)