Specifications

Circuit Descriptions, Abbreviation List, and IC Data Sheets
EN 91ES1E 9.
beginning of the start-up phase, the driver receives its +5V
supply via 3421 and 6465 (see circuit diagram A2). During the
slow start-up phase, the LOT 5450 pin9 voltage gradually
increases, and finally takes over the supply of the +5V voltage,
to supply 5402/7404 via 6403/3493/3451/3419/3432/3415/
3414.
At the end of the slow start-up phase, the deflection stage is
operating at its normal operating condition and all the voltages
are stabilized. Then, the +13V volt supply has fully replaced the
+5V supply to power the horizontal output stage.
At that moment, not only the horizontal deflection, but also the
vertical deflection is functioning at its normal operating
conditions.
9.2.3 Normal Operation and Horizontal Deflection
In normal operation mode, the Hdrive with its 45/55 duty cycle
is switching on and off 7404 (see circuit diagram A2). The driver
stage is working in flyback mode: When 7404 is on, 5402
retains its flux energy and also switches off 7405 via its
secondary coil during flyback mode. When 7404 is switched
off, 5402 releases its energy and turns on 7405. By means of
the on-off switching process, a sawtooth yoke deflection
current is generated.
There are various circuits that are part of the horizontal
deflection circuit.
These will be discussed below:
Horizontal Output Stage:
This a standard circuit (see circuit diagram A2), in which the
main horizontal output stage consists of driver 7404/5402, line
output transistor 7405, tuning capacitor 2411/2414, Scap 2417/
2418 and diode modulator 6404/2413/2416.
Anti-Curtain Effect (Anti-Beta Ringing) Circuit:
5410/2427/3433 (see circuit diagram A2) are the anti-beta
ringing circuit that is tuned to and suppresses the parasitic
ringing frequencies normally occurring in Slot type LOTs to an
acceptable level. For Layer type LOTs, these components are
not required and 9410 is the jumper alternative for Layer type
LOTs.
Beta Ringing, if not suppressed, will cause a type of
interference which is visible as a curtain effect at the left edge
of the screen. This interference is caused by the high amplitude
ringing energy being coupled magnetically or via an electrically
conducting path from the LOT to the small signal circuit. If the
ringing is suppressed to a specific level, the interference will
not be visible anymore.
DAF Circuit:
5455/2402/2403/2405/2406 (see circuit diagram A2) are the
DAF circuit that will be used in DAF or double focus CRT tubes.
For single focus tubes, these components are not required;
9411 is the jumper alternative for non-DAF tubes.
The DAF circuit is used to improve the dynamic focusing of the
tube, particularly in the edge areas. The DC high voltage of
constant level which is supplied to the focus electrode is
referred to as static focus or single focus. In addition to that, an
AC parabolic waveform (derived from the vertical and/or the
horizontal deflection voltages) can be superimposed onto the
DC static focus voltage; this extra AC focusing voltage will then
correct the focus dynamically, corresponding to the scan
position at that particular moment. This is what we refer to as
DAF (Dynamic Astigmatism and Focusing; a method to keep
the electron spot round and focused during the whole scan).
Transformer 5455 takes the horizontal deflection current as its
input and transfers its energy to the capacitor (2402/2403/
2405/2406) on its secondary side. The current in the secondary
coil of the transformer charges the capacitor and this results in
a parabolic waveform. The parabolic waveform is fed to
connector 1402 of the LOT focus cable and is coupled via an
internal 500 pF capacitor inside the LOT and superimposed
onto the static focus voltage.
2nd order S-correction circuit:
5406/2407/3403 (see circuit diagram A2) are the 2nd order S-
correction circuit, which is used mainly in large wide screen
tubes, because they are prone to scanning imperfections that
need 2nd order S-correction. For 4x3 tubes or relatively small
wide screen tubes, these components are not required, and
then 9401 is the jumper alternative for them.
Due to the relatively wide angle of large wide screen flat tubes,
the inner tube surface (which is flat) and the surface scanned
by the electron beam (which is spherical) are very far apart,
especially at the edges. This is because both areas are
nowhere parallel with respect to each other (as they ideally
would have to be). The larger and wider the screen size is, the
more visible the unwanted phenomenon resulting from this
optical misalignment will be. The phenomenon manifests itself,
because the horizontal scanning will be wider at the 1/4 and 3/
4 position, but narrower at the centre and edge position. Note
that this is different from S-correction (correct centre-versus-
edge scanning) and Linearity Correction (correct left-versus-
right scanning).
To carry out the 2nd order S-correction, transformer 5406 takes
the horizontal deflection current as its input and transfers it to
capacitor 2407 on its secondary side. Together with the yoke
coil, capacitor 2407 forms a tuning circuit, and this circuit
modifies the yoke current during the 1/4 and 3/4 scanning
position. In this way, the modified yoke currect compensates
the imperfections that are caused by the CRT geometry.
The function of resistor 3403 is to prevent the secondary circuit
from floating. It pulls DC components of the correction voltages
to gnd.
Dynamic S-correction Circuit (Inner-Pincushion):
5408/5409/2419 (see circuit diagram A2) form the dynamic S-
correction circuit, which is mainly used in relatively large wide
screen tubes. This is, because they are prone to optical inner
pincushion distortions. For 4x3 tubes or relatively small wide
screen tubes, these components are not required; in that case,
9412 is the jumper alternative for them.
As has been explained earlier, due to the relatively wide angle
of large wide screen flat tubes, the inner tube surface (flat) and
the scanning surface (spherical) can never be perfectly parallel
to each other, so optical distortions will be the result, especially
at the edges of the screen. The first imperfection that will
become visible is the phenomenon called pin-cushion
distortion; this can be corrected by the East West circuit for
distortions in the proportions of the top/bottom versus centre
area (distortions in the proportions in the vertical direction have
to be corrected as well, see further down in this text).
Additionally, the larger and wider the screen size becomes, the
more clearly a second unwanted phenomenon will become
visible, called inner pincushion distortion. This happens
because, when two corresponding horizontal scanning lines
are compared, the top one and the centre one will have
different centre-versus-edge scanning length ratios (when the
vertical line at the edge of the screen has been corrected by the
East West circuit, the vertical lines at the 1/4 and 3/4 positions
will still be concave. Note that this phenomenon is different
from 2nd-order S-distortion.)
To correct the dynamic S-distortion, the East West correction
circuit has to generate a deflection current which is higher at
the centre scanning position of the screen than at the top/
bottom positions. With the Bridge coil 5408/5409, this higher