Zenith ZVM-121 Service Manual page 10

Page 3-2
ON/OFF CONTROL (SX201)
This SPST switch is secured to a mounting bracket by
two twist tabs. To remove it, first remove the switch
knob, and then remove the bracket from inside the
cabinet. With pliers, twist the two twist tabs to free the
switch. See Figure
3-1.
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Test - Test this switch with an ohmmeter. Place the
leads across the switch terminals. With the switch in
the OFF position, the meter should read infinite resis-
tance. With the switch in the ON position, the meter
should read zero resistance.
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VERTICAL
HOLD
Figure 3-2
VERTICAL HOLD (R612)
This
250
kfl potentiometer is soldered to the rear of
the chassis PC board. See Figure
3-2.
Adjustment - If the picture rolls upward or down-
ward, adjust the vertical hold control. Turn the con-
trol clockwise or counterclockwise until the rolling
stops.
Test - Test this control by removing it from the cir-
cuit board. Place an ohmmeter across the terminals to
determine if it is open or shorted.
VERTICAL SIZE (R616)
This
300
k!l potentiometer is soldered to the rear of
the chassis PC board. See Figure
3-2.
Adjustment - Adjust this control for proper picture
height.
Test - Test this control by removing it from the cir-
cuit board. Place an ohmmeter across the terminals to
determine if it is open or shorted.