The Output Amplifier Circuit And The Coupling Circuit - NEC MultiSync FP1370 Service Manual

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).
From IC513
1V
R527
58
C520
Integration circuit
R983
C989
+12V
+15V
R953
R951
Q981
Q951
C958
D951
R952
ZD951
C959
From IC510
(Fig. 5.3) The dynamic focus output circuit
3.3V
R528
R529
IC510
R541
IC510
R540
Inverting amplifier
(3times amplifier)
+80V
Q982
R985
D981
R986
D982
Q983
R984
R990
D984
C984
ZD981
8-21
Aprox. 3Vp-p
Q984
R989
C983
Q985
T981
+220V
R991
R993
R992
C986
-80V
To FBT(T5R1)
C985