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ON SCR E EN CI RCUIT
2 . 6
Note: Unless otherwise specified, a l l test points and adjustments are located on the ON SCR E E N board .
Check Point
No.
Item
TP2
1
Character
(TDC)
Position
0
2
Back ground
TPl
Color
(TSC)
0
I F CI RCUIT
2 . 7
Note: U nless otherwise specified, a l l test points and adjustments are located on the IF board.
Item
Check Point
No.
vco
1
MON ITO R
2
A F C
JP1 -5
- -· -
3
Color Level
JP1 - 1 2
1
level =
Y
Magenta level =
0 .45
Fig. 2-7-1
4
R F AGC
M ON ITO R
2-1 0
&
Adjustment
Signal
Parts
C1 5
• E- E
(CH A R A
POS I )
Midpoint
C1 8
• E-E
(BACK
COLO R )
Midpoint
&
Adjustment
Signal
Parts
• TV broadcast
T2
• Tuner mode
(VCO)
T3
• TV broadcast
(AFC)
• Tuner mode
• A F C SW : N O R M
-
• TV broadcast
R40
• Tuner mode
(COLOR
L E V E L )
1
a
:
=
:
b
0.45
R 2 1
• TV broadcast
( R F AGC)
• Tuner mode
Mode
Note : For below adjustments use 1 : 1 probe with
i n put capacitance less than 1 00 p F .
1 . Connect a frequency counter to TP2 ( DTC) (mid
point of R22 a nd R23) and G N D . Short I C l -2 1
pin to G N D and short I Cl -5 pin to I C l -22 pin
(SWD 5 V ) .
2 . Adjust C 1 5 for 8 .7 ± 0 .05 M H z without video
signa l .
1 . Connect a frequency counter to TPl (TSC) (mid- ·
point of R24 a nd R25 ) and G N D .
Adjust C 1 8 for 7 .1 5909 ± 0.0001 M Hz.
Mode
1 . R eceive a color broadcast on a V H F-H I channel
(7 to 1 0 ) .
2. Adjust T2 to obtain a fine picture o n the monitor.
1 . Receive a color broadcast on a V H F-H I channel (7
to 1 0) .
2 . With A F C SW to N O R M, connect oscil loscope to
pin 5 of JPl .
3. Set the oscil loscope to DC mode and adjust T3 to
set the !�edge of the ripple waveform to 4.0 V.
1 . Supply a color bar signa l o n a VH F-H I channel (7
to 1 0) from a TV channel signal generator and
select the channel corresponding to the generator.
2. With AFC SW to N O R M , adjust R40 to prod uce
signal waveform as shown in Fig. 2-7 -1 .
Alternate method:
1 . R eceive a color broadcast on a V H F-H I channel (7
to 1 0) .
2 . With A F C SW to N O R M , adj ust R40 so that the
magenta l evel becomes 2/3% of the sync . leve l .
Note: Adjust R 2 1 ( R F A G C ) to correct for excess
noise in the picture or when streaky cross inter
ference occurs due to strong electrical fields.
1 . Adjust R 2 1 to minim ize noise or streaks o n the TV
screen.
2. Check for absence of abnorma l ity on a l l channels.
Description
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