If the bias angle of a picture widens, the distance from the
center of a picture to each corner becomes farther as it moves to periphery.
This causes the picture being distorted (Picture Lowering) horizontally in a
shape of a spool because of the strong bias at four corners where are the
farthest from the center. E/W is a circuit that corrects the spool-shape on the
left and right part by crossing Parabolic wave form over the horizontal output
board and controls the current which flows through terminal no.47. Parabolic
wave comes out from terminal no.47 of CXA2165 CHROMA IC(IC31) It also controls
the horizontal-related factors of Factory data such as picture size, size
change and Parabola gain change. It has an essential role of minimizing the
picture swaying (High Voltage Regulation).
- E/W Circuit Constitution and Operation Principles.
E/W circuit consists of KA393(comparator), FQP630(output
TR), and other parts. This uses a method in which PWM controls the circuit
using a comparator. The advantage of this PWM Control method is that POWER Loss
hardly occurs and generates little heat when using low H/S. Input E/W signal to terminal no 3,5 of
IC401(KA393) and carrier wave to terminal no 2,6. Carrier wave can be made by
reducing the horizontal collector voltage and integrating the wave form using
D405,R414 and C406. Then the carrier wave is compared with E/W signal in IC401
and outputs PWM (Pulse Width Modulation) wave form. Bias current shall be
controlled using Q404. Picture swaying
occurs as the picture brightness varies. To correct this, control the high
voltage regulation using Q401(1N7000), R433 and C411 That is, Q401 is a circuit
for correcting Static Regulation and used to prevent the picture size changing
as the picture brightness varies. It
detects the ABL voltage and inputs to Q401 Gate through R423 resistance. Then
the ABL voltage change is sent to IC401(KA393) output and controls the DC of 404(FQP630)
Gate terminal, to keep the picture size from changing.
Also, E/W circuit functions as a compensatory circuit
against the picture shaking by reversely compensating the picture swaying. This
is possible by inputting ABL voltage to E/W using R433 as the picture
brightness varies. There are H,V,
PIN-COMP as well in Factory data and these correct the high voltage regulation.
If the H-COMP capacity value increases, correction vector increases too and
this causes a strong picture swaying. On the other hand, if the H-COMP capacity
value decreases, correction vector decreases causing extensive picture size
change. V-COMP, likewise, controls the vertical correction vector and operates
in the same mechanism as H-COMP. PIN-COMP
is a function, which corrects the movement of four corners of a picture. If the
capacity value is excessive, a picture curves outwards when the picture is
bright. COMP capacity value, therefore, should be varied +/- step from the factory-adjusted
condition, since a gain widely varies dependant on the SET distribution.
VERTICAL LINES BEFORE AND AFTER E/W CORRECTION
HRS [Horizontal Raster Shift]
When electron BEAM emanates from CRT, it must form the image
evenly on the center of a screen. However, the left-right linearity can be awry
due to the micro-distortion of horizontal angle while producing CRT. HRS is a
compensatory circuit which crosses DC voltage over CS condenser on horizontal
output board to correct the distortion.
Operational Principle.
HRS circuit consists of R407, D415, D407, SW401, C415, L404.
If switch SW401 (Service S/W) to the direction of R407, it raises the C426 CS
condenser voltage through D415 and the picture moves to right. If switch SW401
to the direction of D417, the picture moves to left.
C415 is functioning as a condenser, which stops generating
current. It can control the left-right movement since the rechargeable voltage
varies as the condenser capacity value varies.
That is, the larger the C415 capacity value becomes, the bigger the left-right
movement will be.
Picture Movement during 0HRS Connection
Direction of SW407 Switch è Center: Not corrected.
èD415 : moves to the right of a picture
è D417 : moves to the left of a picture.
VERTICAL & N/S CORRECTION CIRCUIT
What is a N/S correction circuit
If the bias angle of a picture widens, the distance from the
center of a picture to each corner becomes farther as it moves to periphery.
This causes the picture being distorted (Picture Lowering) vertically in a
shape of a spool because of the strong bias at four corners, which are the
farthest from the center. Crossing Parabolic c N/S Circuit Constitution and
Operation Principle.
Consists of L304, C305, C439, R312. Symmetries the up and
down amplitude using the saturable reactor of L304 and adjust N/S Gain by
controlling the capacity value of C305 and C439. If the correction vector is excessive, one can slightly reduce
the resistance of R312 an make correction effect to the amount of a correction
signal current of a vertical period over the vertical bias current and applying
it.
COMPARISON BEFORE AND AFTER N/S SIGNAL CORRECTION
