98
24. RA-6 Deflection Circuit Troubleshooting
V DEF
V RET
V DEF
V RET
V DEF
V RET
-15V
+15V
R8047
L8003
D8004
C8015
CN8006-3
VDRV+
CN8006-5
VDRV-
R8147
R8041
R8032
R8018
R8014
R8013
+15V
C8001
R8019
R8015
D8001
R8022
Q8001
C8017
CN8007
CN8008
CN8009
CN8006-7
VP
DYR
DYG
DYB
R8022
R8071
R8036
R8039
TH8001
+
1
2
3
4
5
6
7
+
-
IC8003
LA78045
FIGURE 24-2 - VERTICAL DEFLECTION RA-6 CHASSIS
24.2TVP14 1473
6/13/02
1
2
3
1
2
3
1
2
3
Repeat Vertical Output IC Failure: If IC1509 fails immediately upon replacement or in a short amount of time, 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 or it has a problem and
is unable to comply. Due to the nature of the operational amp within IC5004, it is rare for it to be the cause.
Operational amps have massive amounts of gain, which is why they need negative feedback to keep them under
control. Gain problems are most likely to be caused by improper supply voltage (very rare) or problems in the
feedback line. 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 op amp 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 C8017 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.