Dynamic Focus Circuit; The Horizontal Parabolic Wave Generation And Gain Control Circuit; The Vertical Parabolic Wave Generation And Gain Control Circuit; The Output Amplifier Circuit And The Coupling Circuit - NEC MultiSync FP1350 Service Manual

5. DYNAMIC FOCUS CIRCUIT

The dynamic focus circuit section is made up of following three blocks:

1) The horizontal parabolic wave generation and gain control circuit

2) The vertical parabolic wave generation and gain control circuit

3) The output amplifier circuit and the coupling circuit

1) The horizontal parabolic wave generation and gain control circuit
IC501 generates horizontal dynamic focus signal controlled by MPU data based on horizontal frequency
and horizontal screen size. The horizontal dynamic focus signal which is generated by internal logic circuit
is multiplied with vertical period signal which is created by DSP. The multiplier inside IC501 outputs the
horizontal dynamic focus signal modulated with the vertical signal. This signal is output from 8bit D/A
converter at pin 10 after it is converted to analog signal. The output signal at pin 10 is smoothed by noise
filter composed of R501 and C501. After this signal is inverted and amplified approximately 14 times by
IC513, it is sent to the horizontal dynamic focus output circuit.
Aprox. 0.5Vp-p
H.DF. Output
(8bit DAC)
(Fig. 5.1) The horizontal parabolic wave generation and gain control circuit
2) The vertical parabolic wave generation and gain control circuit
The vertical parabolic wave is generated by DSP. IC501 generates vertical parabolic wave by calculation
based on MPU data and outputs vertical dynamic focus correction signal at IC501 pin 58. This signal is
integrated by integration circuit composed of R527 and C520. After this signal is inverted and amplified
approximately 3 times by IC510, it is sent to the vertical dynamic focus output circuit.
1H
R501
10
C501
Noise filter
3.3V
R50G
R50H
IC513
R50K
IC513
R50L
Inverting amplifier
(Aprox.14times )
8-19
Aprox. 7Vp-p