Sony KD-34XBR2 Training Manual page 32

Standby light blinks five times – Picture Blanked (dark), sound OK.
Refer to Figure 8-8 for this circuit and testing.
Circuit - Three IK pulses are measured by Y/C, CRT Drive as they return to IC201/pin 58. Each pulse corre-
sponds to the efficiency of each CRT cathode and is used to adjust the RGB gain within IC3101 to maintain color
balance while the TV is operating (dynamic adjustment). The IK signals originate from IC3101 in as three bright
lines in the vertical-blanking interval at lines 19-21. As the picture tube ages, the IK signals may fall below the
threshold for automatic balance adjustment causing IC3101 to mute/blank the substandard picture. Although the
picture is blanked, the IK pulses still output IC3101 and the three return IK pulses to IC3101/pin 58 are still
operational as long as the TV is ON.
Testing - Increase the G2 control on the CRT' s C board. If that does not return cathode current to within operating
range so the picture appears, examine each filament to see if it is lit.
The next step uses your scope to determine if there is drive signal to each CRT cathode. Begin by looking for a
positive pulse at CN9001/pins 1, 3 and 5 as it enters the C board. Next, check for these signals at each CRT
cathode (R, G and B). If they are present, examine the composite IK signal at CN9001/pin 8 of the C board. You
should see three pulses that change in level as the G2 control is adjusted. One pulse corresponds to one color
and they should be within 15% of each other. The normal IK output from the CRT/C board is about 1Vp-p pulses
at pin 8. If these three pulses are present at pin 8, the problem is on the A board about IC3101.
Q3101
64
Q3102
63
Q3107
IC3101
62
Y/C CRT
DRIVE
CXA2150AQ
C3117
0.068
58
A BD.
FIGURE 8-8 - BLANKING - 5X INDICATION
VIDEO
OUTPUTS
CN3101/
CN9001
IC9001
1
R
G
IC9002
3
B
IC9003
5
Q9001
R3122
8
IK
R9013
C3115
0.002 C BD.
29
8. Protection Block (HA-3 Chassis)
R CRT
CATHODE
7
G CRT
CATHODE
7
B CRT
CATHODE
7
Q9013
R9036
Q9015
R9041
R9042
Q9007
19TVP12 1336 9/4/01