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No raster, no sound (81 is abnormal)
NOTE
1702 locations in (
). The regulator PCB assembly used in 1702 models differs from the 1701
power PCB assembly. The B1 voltage circuits should be checked beginning with IC901.
[Cause]
Abnormal B1 voltage indicates trouble in the power supply circuit. When B1 voltage is not only low
but also abnormally high, X701 (Q501) of the X-ray protector is turned on, setting the collector voltage
to 0 V. The horizontal oscillator is then disabled resulting in no raster and no sound.
1 .
When D 105, R 105, R 108, R 109 are open, the base voltage of X 101 and X 102 rise to increase
B1 voltage to more than 130V. This causes the X-ray protector to work, resulting in no raster.
2.
If the base voltage drops as when R103 is open or C105 is shorted, the B1 voltage is reduced
to less than 40 V. This will mostly result in no raster, no sound.
3.
When the B1 voltage drops to about 70 V, because R91 0 is open and D1 05 is shorted, the screen
becomes dark and the raster size is reduced because of insufficient horizontal and vertical
amplitude.
C
START
)
!
Does 4.0A fuse blow?
,NO
~
YES
Can B1 be adjusted to 110 V with
Rectifier including power supply
I
B1 ADJ R109?
transformer has failed.
YES
r - - - - - - - - - - - - - - - - - - - - - - 1 N O
Misadjustment Horizontal deflection
l
Does the base voltage at X101 change
I
circuit has failed when picture is
with B1 ADJ R109?
small with B1
=
110 V.
t
NO
t
YES
Is the emitter voltage of X102
Does the emitter voltage of X10'1
correct?
change with B1 ADJ R109?
+
ABNORMAL
t
NORMAL
=
6.6V
NO
~
t
YES
D105 open or short
I
X102 open or short, R105, R108,
X101, R103
I
X02 has
I
R109 open. C105 short
open
failed
18
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