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Service Adjustments
I
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 omosite
direction
until the snow iust disarmears.
.,
—.
(1) Connect DC meter to R791 and the ground.
Set the +Bl adjustment
control (VR551 ) 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 (VR551 ) for 130
* 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) Receive 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 normal, the colour to
minimum.
(3) Set the service switch (SW220) at the service side.
(4) Connect a oscilloscope
to TP - 6C(+) and TP - 6F(- ).
(Probe attenuation =$10 :1, Sync. V- sensitivity40.05V
Signal coupling @ DC)
Using VR640, adjust "a" ------------
- ~
to be OV.
+–:v
(5) Set
the
drive
volume
(VR602
and
VR612)
at their
mechanical
center.
(6) Set the
bias
volume
(VR601,
VR621
and
VR611 ) to
minimum. (fully counter clockwise).
(7) Turn the screen volume
on the FBT to obtain just visible
one coloured line.
(8) Adjust each bias volume (VR601 - blue, VR621 - green and
VR611 - red) alternately
until a dim white line produced.
(9) Set the service switch (SW220) at the normal side.
(1 O) Adjust the drive volume
(VR602 - blue and VR612 - red)
alternately to produce normal black and white picture.
(11 )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 maximum.
(3) If the picture is too wide or narrow, cut or short the "AJ1" on
the
main
unit.
When
AJ1
is shorted,
the
horiz.
width
increase. When AJ1 is cut, the horiz. width decrease.
Important
Note:
If AJ1 is cut, its gap must be more than
'J'+l=;:::;;%sparks'
(4) Connect
a high voltage
probe to anode
lead
of the picture
tube,
(5)
The high voltage must be between 20-22KV(14"
16"),
24- 26 KV(20" 21 ").
NOTE: If the picture tube is replaced, check the high voltage.
The horiz. width adjustment
affects the high voltage and
sub brightness.
Therefore,
recheck the sub brightness
and the high voltage.
–7–
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