Sony KDP-57XBR2 Training Manual page 82

Repeat Vertical Output IC Failure: If IC1509 fails immediately upon replacement or soon thereafter; it is usually
the fault of C8015. This is the boost capacitor. It charges to almost 30VDC during the lower half of the vertical
sweep to provide additional voltage to allow the beam to retrace to the top rapidly. When this filter dries out or
opens, the output IC will attempt to accomplish the retrace but the negative feedback line will resist the sudden
voltage kickback from the yoke and the +15V drive will cause the IC to draw excessive current. In smaller
televisions, a boost capacitor failure causes slight loss of vertical at the top with some fold-over.
Insufficient Vertical Height: Either the vertical output IC is being told what height to display and is unable to
comply, or it is receiving erroneous drive information. Due to the nature of the operational amp within IC5004, it
is rare for it to not be able to amplify properly. Operational amps have massive amounts of gain, which is why
they need negative feedback to keep them under control. Suspect IC5004 as the last possible cause. Gain
problems can be caused by improper supply voltage (very rare) or problems in the feedback line (more likely).
This is why you should always scope the feedback line when height or linearity problems arise. In this chassis,
the best point is the top end of the ground return resistors (R8036 or R8039). What should normally be here is
approximately 1VPP of vertical rate sawtooth. If there is a problem, you will observe one of two things: A
significantly larger sawtooth level or horizontal frequency contamination in the sawtooth. A large sawtooth indicates
one or more of the ground return resistors or the thermal compensator TH8001 has opened. The negative
feedback of the operational amplifier will respond by reducing gain. If there is a large amount of horizontal
component in the feedback, the amp will also reduce gain since the average DC level will be higher at this
frequency. The vertical deflection yoke windings are right next to the horizontal windings so it is very easy to
induce this into the vertical return. Suspect an open C8001 or C8023 at this point.
Should the feedback line check OK, you now have a possible input problem. IC3006 can cause this and it is
difficult to verify without replacing it. Beware that faulty NVM ICs have been known to cause vertical height
problems.
STBY LED
IC001
MAIN MICRO
M306V2MF
AC RELAY
(B BD.)
B BOARD A BOARD
S DATA
B19
31
R055
R069
26 A20
S CLK
CN013/
CN3022
FROM
+15V
SEC
P.S
(G BD.)
D BOARD
FIGURE 18-2 - VERTICAL DEFLECTION RA-5A CHASSIS
18. RA-5A Deflection Circuit Troubleshooting
25
IC3006
VIDEO
PROCESSOR
CXA2150AQ
35
24
52 53
- V
+
DRIVE
3 5
CN3005/
CN8006
D8001
5.6V
7 1
2
IC5004
V OUT
-15V 4
LA78045
5
79
V PROTECT
CN3103/
CN5505
7
Q8001
BUFF.
V DY
CN8009
R8015
R8036
CN8008
CN8007
3
R8039
1
2.2
3
R8040
220 1
3
1
18.2TVP14 1462
B
G
R