Horizontal Phase Shift Circuit; Horizontal Drive Circuit - Tatung OMNISCAN SERIES Service Manual

be tuned during the set up procedure.
For 64KHz, 48KHz and 31KHz mode, R420, R413 and
R422 is adjusted sequentially.
/
Note that the network values are chosen so that R420,
R413 has negligible in the 64KHz mode. In the low
frequency mode, it adds to the effect of R422,
therefore, during setup, it is advised that the high
frequency operating modes be optimized first.
ALIGNMENT PROCEDURE
64KHz
--------->
48KHz
--------->
31 KHz
(R422) (R413) (R420)
HORIZONTAL PHASE SHIFT CIRCUIT
16V~--------------------~--~
C414
R4.'9 R440
J
U
56K 68K
sov
R441
H.POSli 10M
1~ I~
NP 3.31<
R444
10K
1/4W
3.16 HORIZONTAL PHASE SHIFT CIRCUIT
(Refer to circuit diagram Fig-16)
An adjustable delay is introduced at the phase shift
pin 2 of 0403.
The phase control signal is derived from pin 5 of P401
and fed into 0402a to achieve good noise rejection,
the phase control is achieved by making use of the
0404, 0423a and relative components.
For the 31KHz operating modes, analog switch 0423a
is on to optimize the picture phasing in the low
frequency operating mode.
R448
10K
MODEl
R451 C413
68K II81J
sov
040.)
LA78S1
Fig-16
CONTROL
~1-¥1.'-"'--I
FROM R442
MICRO
BOA~D
C4!S 20K D403 R44 D402
O.22U~ ___ J~~h- __ ~ ____ +-IN~4~1_4~8_2~2~O~~!N~4
__
14_84
R4%
I
lOOK
I';
..,.
50\1
r
1
4
,... ,.....I .....
0423d
5 TC PHASE
R445 C416
IioK
I
l04z
I,. 50V
12V
40G6 5W
3
C412 I
IOIJ
sov
~J
3.17 HORIZONTAL DRIVE CIRCUIT
proportional to the primary drive voltage.
(Refer to circuit diagram Fig-17)
The product is designed around a COMMON base-
drive circuit driving separate horizontal deflection and
HV. OUTPUT circuit, to provide sufficient switching
current.
0413 is switched by the horizontal drive signal from
0403 via network 0408-0409.This produces a
sufficient voltage to T400.
HORIZONTAL DRIVE CIRCUIT
Z4V
Fig-17
t1.SIZE
CONTROL INPUT
FROM MICRO BOARD
R458
t
R459
UK I BK
P.460 <'420
'8K
10~Z
Snubber network R463-C422 compensates for
leakage inductance in T400 and shapes the base
drive waveform.
-'Wv-+---AM.---......
. 150V
The drive current of Hor. output 0411 is automatically
compensated by network 0410-0422a-R456. Pin 2
of 0422a receive a raster width control voltage and a
dc voltage is giving to the base of 0410 via pin 1. So
when raster width is changed the primary windings of
T400 Will receive different drive voltage via 0410.
The result is that the current in secondary winding is
=
3-14
=
!l456
120
2W
!l463
220
1/4W
C422
T
222J
SOY
f