Digital Dynamic Convergence Clear (Ddcc) Circuit - NEC FP1355 Service Manual

<Vertical magnetic field canceling function>
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 display surface, and the
adjustment is done by DC current according to the value displayed on OSD 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 IC101 pin 4 (PWM-DAC), and DC current
of +/-140mA (max) is made to flow to the speed modulating coil by IC804 pin 8.
1.5.4

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 compen-
sated 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 wave-
form that flows to the coil of the electric magnet.
(See Fig. 18)
(1) Production of compensation current waveform
There are 30 kinds of compensation elements, and they are programmed in
IC601(CP267P151=uPD61882BGC) one by one by using the functions. The amplitude of
the current is controlled by inputting the compensation coefficient into the function.
2
YHTT= b11T¥y^
2
YHTB= b11B¥y^
YHJT= b12T¥y
YHJB= b12B¥y
2
YHT=b11T¥y^ +b11B¥y^
YHJ=b12T¥y+b12B¥y
@ @ @ @ «
4H_SC=all¥(YHT+YHJ)
b11T
b11B
2
b12T
b12B
Figure 17 DDCC compensation image
1 - 31
V
V
YHTT&YHTB
b11T
b11B
YHJT&YHJB
b12T
b12B
Red F
Blue F