92
20. RA-5A Chassis Protection Block
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.
Then use your scope to examine the signal at the cathode. Go to CN3011/pins 1, 3 and 5 to see if there is a drive
signal going to the C boards. Next, check for these signals at each CRT cathode. If they are present, examine
the IK signal into the A board at CN3011/pin 9. You should see three pulses that change in level as the G2 control
is adjusted. One pulse corresponds to one color and should be within 15% of each other. The normal IK output
from the CRT/C board is about 1Vp-p pulses at pin 9. If these three pulses are present at pin 9, the problem is on
the A board about IC3006.
Standby light blinks six times – TV Shutdown
Refer to Figure 20-10 for this circuit description and testing.
Circuit – IC001/pin 43 monitors the Sub 6.5Vdc from the Primary power supply (G Bd) to the Q box (QM and QI
boards). A short or excessive voltage on the Q6.5Vdc line will cause IC001 to shut off the AC relay (IC001/pin 69
goes LOW), shutting down the TV and blinking the LED six times.
1k
BUFF.
IC3801
VIDEO OUT
IC3701
VIDEO OUT
TDA612OQ
IC3006
VIDEO
PROCESSOR
CXA2150
61
64
26
63
62
58
8
5
1
9
3
2
7
6
12
1
4
2
2
2
12
7
2
1k
BUFF.
IC3901
VIDEO OUT
12
7
2
2
2
2
2
Q3049
CN3803
CN3702
+12V
OUTPUT
CG BD.
CN3805
R
G
B
IK
R3045
R3227
Q3022
BUFF.
+12V
CN3903
R3801
Q3901
LIMITER
OUT
CN3011
CN3703
+12V
N CH
D3709
R3726
R3729
4.7k
OUTPUT
TO RED
CRT
Q3702
IK BUFF.
R3727
220k
CN
3703
CB BD.
CN3909
CN3804
Q3048
Q3050
R3071
R3070
R3069
R3068
R3066
R3067
+9V
+9V
LIMITER
Q3053
Q3056
Q3055
Q3054
P
N
N
N
R3055
C3017
R3228
R3230
Q3021
Q3020
IK
R3229
N
P
P
+9V
+9V
+
- LIMITERS
25
S CLK
S DATA
FROM
MAIN
MICRO
IC001
(B BD.)
+12V
IC3014
CR BD.
+
A BD.
FIGURE 20-9 - PROTECTION-5X INDICATION - RA-5A CHASSIS
9/4/01
31TVP12 1348
Содержание KD-34XBR2 - 34" Hdtv Fd Trinitron Wega
Страница 77: ...74 RA 5A Chassis Board Layout ...
Страница 108: ...APPENDIX ...