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Service Adjustments
SAFETY PRECAUTIONS
:
An isolation transformer
should be connected in the power line between the receiver and the AC
line before any service is performed on the receiver.
X-RADIATION
PRECAUTION
The primary
source
of X-RADIATION
in television receiver is the picture tube. The picture
tube is specially constructed
to limit X-RADIATION
emission.
For continued X-RADIATION
protection, the replacement
tube must
be the same type as the original
including suffix letter. Excessive high voltage may
produce potentially
hazardous
X-RADIATION.
To avoid such hazards, the high voltage must be maintain
within specified
limit.
Refer to this service manual
for specific high
voltage limits. If high voltage exceeds specified limits, take necessary corrective action. Carefully follow the instructions for + B1 volt
power supply adjustment,
and high voltage check to maintain the high voltage within the specified limits.
.
NOTE; Do not attempt this adjustment
with weak signal.
(1) Tune
the receiver
to most
clearest
(or strongest)
VHF
station
in your
area.
Set the
brightness
and
contrast
controls to maximum.
Set the colour control to minimum.
(2) Set AGC (VR1 20) control to mid- range.
(3) Turn AGC control in direction which causes snow to appear,
then in the opposite direction until the snow just disappears.
(1) Connect DC meter to R761 (VR351 side) and the ground.
Set the +Bl adjustment
control (VR351 ) to mid- range.
(2) Set the brightness and contrast to normal.
Tune the receiver to an active channel and synchronized
picture.
(3) Adjust +Bl
adjustment
control(VR351)
for 140 t
0.5 volt
DC.
(1) Receive the monochrome
circular pattern.
(2) Set the brightness and contrast to normal.
(3) Adjust VR401 for optimum horizontal center position,
Horizontal
center
(1) Receive the monochrome
circular pattern.
(2) Set the brightness and contrast to normal.
(3) Vertical centering can be adjusted by switching SW451.
ical center
(1) Re:eive the monochrome
circular pattern.
(2) Set the brightness and contrast to normal.
(3) Vertical size can be adjusted by using VR451.
rtical size
(1) Receive the monochrome
circular pattern.
(2) Set the brightness to normal and contrast to maximum.
(3) Adjust the focus control on the F.B.T for the best focus on
the screen center,
(1) Receiver the monochrome
circular pattern.
(2) Set the brightness and the contrast
to maximum.
(3) Set
the
drive
volume
(VR761
and
VR781 ) at their
mechanical
center.
(4) Set the
bias
volume
(VR762,
VR772
and
VR782)
to
minimum. (fully counter clockwise).
(5) Set the service switch (SW220) to the service side.
(6) Turn the screen volume
on the FBT to obtain just visible
one coloured line.
(7) Adjust each bias volume (VR782-
blue, VR772-
green and
VR762- red) alternately
until a dim white line produced.
(8) Set the service switch (SW220) to the normal side.
(9) Adjust the drive volume
(VR781 - blue and VR761 - red)
alternately to produce normal black and white picture.
(1O)Check
for proper
grey
scale tracking
at all brightness
levels.
NOTE : If the grey scale adjustment
is made after picturetube
replacement,
check high voltage
and sub - brightness
adjustment.
(1) Receive the monochrom
circular pattern.
(2) Set the brightness and contrast to normal.
(3) If the picture is too wide or narrow,
adjust the horizontal
width using VR462.
NOTE: The horiz, width adjustment
affects the high voltage,
Therefore,
recheck the high voltage,
(1) Connect a high voltage probe to anode lead
of the picture
tube.
(2) Receive the monochrom
circular pattern.
(3) Set the brightness and contrast to maximum.
(4) The high voltage must be between 28-30
t 1KV.
NOTE: If the picture tube is replaced, check the high voltage.
-7–
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