Production Of Compensation Current Waveform; Waveform, And Operation On The Picture; Adjustment Method - NEC DPro2070SB Service Manual

1.4.6.1 Production of compensation current waveform

There are 30 kinds of compensation elements, and they are programmed in IC601 one by one using the
function. Inputting the compensation coefficient into the function controls the amplitude of the current.
Fig. 6 DDCC compensation image
Examples of the functions and current waveform/compensation operation of YH (YHTT, THTB, YHJT,
YHJB) are shown as follows.
In the above formulas, b11T, b11B, b12T and b12B express the compensation coefficients, and y and y^2
express the primary and secondary functions of the vertical frequencies.
The other parts except the compensation coefficients are programmed, and desired amplitudes (=
compensation amount) are gained by varying the coefficients.
YHTT and YHTB compensate the upper and lower parts of the picture of the characteristic components of
their DYs to compensate the upper and lower parts of the picture of the axis deviation component.
component gained by adding YHT and YHJ is multiplied by the offset compensation coefficient a11.
resultant component is regarded as 4H_SC, and is output from IC601 pin 61.

1.4.6.2 Waveform, and operation on the picture

The case in which the currents flow through 4H coils of the sub yoke is explained. Regarding YHT
(secondary function in the vertical frequency), in case of Fig. 6 as an example, the current is large in the
same direction at the start (upper end of the picture) and the end (lower end of the picture) of the vertical
frequency, and is zeroed on the X axis of the picture. Therefore, the magnetic field that is proportional to it
is generated, and RED and BLUE vary in the same direction only at the upper and lower ends of the picture.
As aforementioned, YHT can be independently controlled at the upper part (b11t・y^2) and lower part
(b11B・y^2).
Moreover, regarding YHJ (primary function in the vertical frequency), if the flowing direction of the current is
opposite at the start (upper end of the picture) and the end (lower end of the picture) of the vertical
frequency as an example, RED and BLUE vary in the opposite direction only at the upper and lower ends of
the picture. Making the current flow to the 4V coil can do compensation in the vertical direction.
Fig. 8 (a) and (b) shows the image of each adjustment item of the DDCC adjustment.

1.4.6.3 Adjustment method

Before the adjustment with the compensation circuit, it is necessary that they are properly adjusted at the
center (H-STATIC and V-STATIC), on the X axis (XH slider, B-Bow 4P, XV differential coil) and on the Y axis
(YH volume, YV volume).
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