NEC MultiSync FP1350 Service Manual page 168

Aprox. 1Vp-p
V.DF. output
(1bitDAC)
(Fig. 5.2) The vertical parabolic wave generation and gain control circuit
3) The output amplifier circuit and the coupling circuit
The horizontal and vertical parabola waveforms output from IC501 are clamped before each output
circuit for wide dynamic range of the output circuit. The clamp voltage is determined by the voltages of
ZD951 (for the horizontal parabolic wave) and ZD981 (for the vertical parabolic wave).
After the clamp circuit, the horizontal parabola waveform is amplified approximately 12 times by Q981.
The output signal at Q981 collector is input to T981 via the buffer circuit which is composed of Q982,
Q983, Q984 and Q985. The gain of T981 is approximately 9. The vertical parabola waveform is
amplified approximately 80 times by Q987. The output signal at Q987 collector modulates the secondary
winding of T981 as the vertical parabola waveform. Therefore, T981 outputs the horizontal parabola
waveform which is modulated by the vertical waveform. This modulated waveform is input to the CRT
focus grid via the built-in capacitor of T5R1 (FBT).
R953
From IC513
Q951
R952
1V
R528
R529
R527
58
C520 IC510
Inverting amplifier
Integration circuit
(3times amplifier)
+80V
R983
C989
+12V
+15V
D981
D982
R951
Q981
C958 D951
ZD951
C959
From IC510
(Fig. 5.3) The dynamic focus output circuit
3.3V
IC510
R541
R540
Q982
Q984
R985
R989
R986
Q985
Q983
+220V
R984
R991
R990
D984
C984
ZD981
C986
8-20
Aprox. 3Vp-p
C983
To FBT(T5R1)
T981
R993
C985
R992
-80V