6-7
V20 Chassis Technical Training
and Troubleshooting Guide
If X-Ray Protect shuts the TV Off,
pressing the Power button will turn
the TV back On (it may shut Off
again if the problem still exists). If
Arc Protect is activated the TV must
be switched Off before it can be
switched back On.
Vertical Deflection
Figure 6
shows the Vertical Deflec-
tion circuitry. The Vertical Deflec-
tion Generator in the VCJ outputs
push-pull type of vertical deflection
drive signal. +VDR at pin 53 and
–VDR atz pin 52. Both signals are
applied to the Vertical Output IC,
IC4B01. The amplified output from
IC4B01 is directed to the vertical coils in the Deflection
Yokes.
Feedback from the Deflection Yokes ground return at
pin 4 of DY, to pin 1 of IC4B01, provide linearity and S
correction.
The vertical saw tooth, across R4B12 and
R4B10 is directed back to pin 35 of
IC2V00. Pin 35 is the V-Protect Input, if
the saw tooth is missing, IC2V00 removes
all RGB drive to the CRTs.
Deflection Loss Detection
To prevent damage to the CRTs, the TV
must shut Off if deflection is lost. The De-
flection Loss Detection circuit is similar to
previous models, as shown in
Figure 7
.
Q4B01 monitors vertical deflection, and
Q5A38 monitors horizontal deflection. The
conduction of both transistors holds their re-
spective collector voltage below the forward
bias point of the diode in their collector
circuit's (D4B04 or D5A12).
If either Q4B01 or Q5A38 stop conducting, indicating
a loss of deflection, the increase in that transistor’s col-
lector voltage drives the V-Blank line High. The V-
Blank line goes to the CRT Protect circuitry and imme-
diately removing all drive to the CRTs.
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