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Service Adjustments
I
SAFETY PRECAUTIONS
:
An isolation transformer shouldbe connected inthe power line between the receiver and theAC
line beforeany service isperformedon the receiver.
X-RADIATION
PRECAUTION
The primary source of X-RADIATION intelevision receiver isthe picture t ube.The picture
tube isspecially c onstructed to limit X -RADIATION
emission. For continuedX-RADIATION
protection, the replacementtube must
be the same type as the original including s uffix l etter. Excessivehighvoltagemay
produce potentially
hazardous X-RADIATION.
To avoid such hazards,the high voltagemust be maintainwithin specified limit. Refer to thisservicemanual forspecific h igh
voltagelimits. If highvoltageexceeds specified l imits, take necessarycorrective action. C arefully f ollow the instructions
for+ BI volt
power supplyadjustment, and highvoltagecheck to maintain the highvoltage within the specified l imits.
NOTE; Do notattemptthis adjustmentwithweak signal.
(1) Tune the receiverto most clearest(or strongest) VHF
stationin your area, Set the brightnessand contrast
controls t o maximum.
Set the colour control t o minimum.
(2)Set AGC
(VRl 20) control to mid- range.
(3)Turn AGC control indirection which causes snow to appear,
then inthe oppositedirection until t he snow just disappears.
(1)Connect DC meter to R791 and the ground.
Set the +Bl adjustmentcontrol (VR551 )to mid-range.
(2)Set the brightness and contrast to normal.
Tune the receiver to an activechannel and synchronized
picture.
(3)Adjust+Bl adjustmentcontrol (VR551 ) for 130 * 0.5 volt
DC.
(1)Receivethe monochrome circular pattern.
(2)Set the brightness and contrast to normal.
(3) AdjustVR401 foroptimum horizontal centerposition.
Horizontalcenter
(1)Receive the monochrome circular pattern.
(2)Set the brightness and contrast to normal.
(3)Vertical c entering can be adjustedby switching SW451
ical center
(1)Receivethe monochrome circular pattern.
(2)Set the brightness and contrast to normal.
(3)Vertical sizecan be adjustedby usingVR451.
rtical size
(1)Receivethe monochrome circular pattern.
(2)Set the brightness t o normal and contrast to maximum.
(3)Adjustthe focus control on the F.B,T forthe bestfocus on
the screencenter.
(1)Receiverthe monochrome circular pattern.
(2)Set the brightness and the contrastto normal,the colour to
minimum.
(3)Set the service switch(SW220) atthe service side.
(4)Connect a oscilloscope toTP- 6C(+) and TP- 6F(- ).
(Probeattenuation *10:
1,Sync.V- sensitivity
40.05V
Signalcoupling d DC)
Using VR640, adjust"a" ---"------"-"-"--" - - ~
to be OV.
l_llY":
(5)Set the drive volume
(VR602
and VR612)
at their
mechanicalcenter.
(6)Set the bias volume (VR601, VR621
and VR611 ) to
minimum. (fully counterclockvke).
(7)Turn the screen volume on the FBT to obtainjustvisible
one colouredline.
(8)Adjusteach biasvolume (VR601 - blue,VR621 - green and
VR611 - red)alternately until a dim whiteline produced.
(9)Set the service switch(SW220) atthe normal side.
(1 O)Adjustthe drivevolume (VR602- blue and VR612 - red)
alternately
to produce normal blackand whitepicture.
(11 )Check for proper grey scale trackingat allbrightness
levels.
NOTE:
If the grey scaleadjustmentismade after picturetube
replacement, check high voltageand sub - brightness
adjustment.
(3)If the picture istoo wide or narrow, cutor shortthe "AJl"on
the main unit.When
AJl is shorted,the horiz.width
increase. W hen AJl iscut, the horiz, w idthdecrease.
ImportantNote:
If AJl iscut, its gap must be more than
5mm to preventsparks.
%2i!ir"0rethan5
(4)Connect a hig~voltageprobe to anode lead ofthe picture
tube,
(5)The highvoltage must be between 20- 22 KV(14° 16),
24- 26KV(20" 21").
NOTE: If the picture t ube isreplaced, check the highvoltage,
The horiz. w idthadjustmentaffects t he highvoltage and
sub brightness, T herefore, recheck the sub brightness
and the hiahvoltaae.
–7–
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