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and an external bias supply, control can be maintained. If both of the conditions
are met then the trouble is definitely A.G.C. If only one test is passed then
the trouble must be peculiar to the l.F. stage under test.
TROUBLE SHOOTING VERTICAL SWEEP CIRCUITS
The following steps should be taken when checking the vertical deflection
systems. We will .assume that the indications on the television receiver screen
to be tested reveal that there is no vertical driving voltage being delivered
to the vertical winding of the deflection yoke resulting in a horizontal line on
the picture tube.
In order to isolate the defects in a receiver between the vertical oscillator
stage and the vertical output stage, proceed as follows:
+
VERT.
YOKE
C-1
SYNC
_,.,
+
IN
VERT.
-=- LINEARITY
Figure 13
Vertical Deflection System
1. Using the Vertical Grid Drive pulse available on the front of the
Television Analyst, apply this signal to the vertical output stage
grid (see Fig. 13). If, when this signal is applied, the image develops
vertical deflection, then we know that the proper driving signal is
not being supplied to the output stage by the vertical oscjllator. The
defect is either in the oscillator itself or in the capacitor (C-3)
coupling the oscillator to the output stage. However, if vertical
deflection of the image does not occur when the signal is injected
at the grid of the output stage, the defect is located somewhere be
tween this grid and the deflection yoke.
The grid driving pulse signal may not necessarily result in linear·
deflection on the screen of the television receiver. However, we are
primarily interested in the presence or lack of deflection. A closer
approach to good linearity can be obtained by adjusting the linearity
control in the receiver (R-8) in Fig. 13 and by adjusting the Vertical
Drive Amplitude control located on the front of the Television
Analyst. In all cases this control should be at maximum when first
starting to troubleshoot vertical deflection systems.
2. Assuming that no vertical deflection results when the signal is in
jected at the grid of the output stage, inject the Vertical Plate Drive
pulse from the Television Analyst at the plate of the vertical output
25
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