Sharp 8C221, Service Manual

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WHITEBALANCE ADJUSTMENT
The purpose of this procedure is to the picture
tube to obtain good black and white picture at all brightness
levels while at the same time achieving maximum usable
brightness. Normal RF
setting and purity adjustments
must this procedure.
This adjustment is to be made only after a warm-up
operation is provided for minutes at least.
With antenna connected to the receiver, tune in picture
on a strong channel.
Rotate the
control to maximum
position and misadjust Tuning so that the receiver
will not produce a color picture while the following
adjustments are being performed.
Set the Green Drive and Blue Drive
controls to mid-position.
Rotate the Red, Green and Blue Bias controls to the full
end of their rotation ranges.
Set the Service Switch, on to Service position.
Rotate the Screen control to the full
end of its rotation range. Then, rotate it until a
dim raster of one pronounced color (Red, Green or
Blue) is obtained.
The other two color Bias controls must be rotated
until a dim white raster is obtained.
Set the Service switch to Normal position
Set the Brightness control
to maximum.
Set the two Drive controls to obtain best white uni-
formity on the picture tube screen.
Rotate the Brightness control to minimum.
Rotate the Brightness control to clockwise until a dim
raster is obtained.
Touch-up adjustment of the three Bias Controls to
obtain best white uniformity on the screen.
Black and white tracking procedure must have been com-
pleted before attempting this adjustment.
Operate receiver for at least minutes and with antenna
connected to the receiver, tune in picture on a strong
channel.
Connect voltmeter positive probe to and negative
probe to on
Rotate Brightness and Contrast controls to maximum.
Adjust
contrast control to obtain a reading
of
PURITYADJUSTMENT
Before purity adjustment can be made, the receiver
should be demagnetized and allow to run with full bright-
ness (without bloom) for a minimum of minutes and
static convergence must be correct.
With antenna connected receiver.
Fully turn the R-Bias
and B-Bias
controls counterclockwise to get green alone.
Loosen the clamp screw for deflection yoke and draw it
back as much as possible.
Turn the purity magnet rings and them so that a
green band is produced and that red and blue bands are
made at the right and left.
Slowly slide the deflection yoke forward and it by
tightening up the clamp screw when the best over-all
green is obtained in the screen.
When purity is not achieved, repeat the steps 4 and
then the best purity can be obtained.
Fully turn the G-Bias control counterclockwise
and then the R-Bias control clockwise. Check if the
purity of red has been achieved. After that, check
the purity of blue as well.
YOKE
H-SIZE COIL
MAGNET
PURITY MAGNET
Figure
CONVERGENCEADJUSTMENT
Any impurity induced as a result of relocation of
the receiver normally will be removed by the Automatic
Operation.
The recurs any time
the receiver is turned on, after being off for at least 5
minutes.
The receiver, with the Brightness and Contrast controls
in normal position, should be operated for minimum of
minutes before proceeding. Also, adjustments such as
purity, vertical size and vertical linearity must be made,
as directed in this manual, before attempting convergence
adjustment.
Connect the cross pattern Generator to the VHF
antenna terminals of the receiver and turn the receiver to a
channel suitable for operation with the particular generator
being used.
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