Controls - Zenith ZVM-121 Service Manual

Page 3-1
CONTROLS
BLACK LEVEL (R204)
This
2
Mil potentiometer is secured to a mounting
bracket by two twist tabs. To remove the control,
remove the bracket from inside the cabinet. Then
remove the control knob and, with a pair of pliers,
turn the two twist tabs to free the control. See Figure
3-1.
Adjustment - Adjust this control for a screen that is
comfortable to the eye.
Test - Test this control with an ohmmeter. Place one
lead on the middle terminal and the other lead on
either outside terminal. Then rotate the control and
observe the meter. If the reading is infinite or zero, the
potentiometer may be open or shorted. NOTE: It may
be necessary to disconnect the wires on the outside
terminals.
I
CONTRAST CONTROL (R203)
This
1
kfl potentiometer is secured to a mounting
bracket by two twist tabs. To remove the control,
remove the bracket from inside of the cabinet. Then
remove the control knob and, with a pair of pliers,
turn the two twist tabs to free the control. See Figure
3-1.
Adjustment - Adjust this control for a screen that is
comfortable to the eye.
Test - Test this control with an ohmmeter. Place one
lead on the middle terminal and the other lead on
either outside terminal. Rotate the control and ob-
serve the meter. If the reading is infinite or zero, the
control may be open or shorted. NOTE: It may be
necessary to disconnect the wires on the outside ter-
minals .
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/..../
/
BLACK LEVEL
CONTROL
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CONTRAST
CONTROL
J
ON/OFF
SW ITCH
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Figure 3-1