Service manual

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12
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. The
component gained by adding YHT and YHJ is multiplied by the offset compensation coefficient a11. The
resultant component is regarded as 4H_SC, and is output from IC601 pin 61.
1.4.3.2 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.
1.4.3.3 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).
Though DC current is superimposed on the sub yoke, H-STATIC and V-STATIC are pushed to the greatest
possible extent by the adjustment with CP ring in order to reduce the stress of the driver IC8A1 (STK391-
110).
Moreover, since 4H and 4V coils alone are installed on the chassis, it is first necessary that the
convergence of RED, BLUE and GREEN (6H, 6V) satisfy the specifications for the performance of ITC
(CRT&DY).
As the adjustment procedure, the adjustment values of 30 elements are not respectively zeroed but they
are adjusted to nearest to zero with a total balance in good order.
In other words, the balance (compromise) adjustment with each adjustment item is applied.
The correspondence of the names of DDCC adjustment mode to the coefficients of all 30 elements is
shown below.
1.4.3.4 Block diagram
Fig. 9 shows the block diagram of the DDCC circuit.
The components 4H_DC (pin 6), 4H_SC (pin 61), 4V_DC (pin 8) and 4V_SC (pin 60) supplied from IC601
to 4H-Coil and 4V-Coil are output, the dynamic component (4H_DC, 4V_DC) is amplified with IC6A2, and
the static component (4H_SC, 4V_SC) is amplified with IC6A3.
DDC (pin 7) output from IC601 and DEFL_+3.3V (pin 3) output from IC602 are respectively the reference