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This same pulse is transformer-coupled to the secondary of transformer T2
where it is rectified by CR2, CR106, and CR105 to produce rectified voltages
of approximately 12 KV (9 and 12 inches) or 9 kV (5 inches), "C" VDC, and
"B" VDC respectively. 12kV or 9 kV is the anode voltage for the CRT, and "C"
VDC serves as the source voltage for grids No. 2 and 4 (focus grid) of the CRT
The "B" VDC potentail is the supply voltage for the video output amplifier, QlOl.
Section 3
PRELIMINARY ADJUSTMENTS
3.1
SYNCHRONIZATION AND DRIVE SIGNALS
Apply horizontal and vertical drive signals to the horizontal and vertical drive
terminals as indicated on your schematic. Adjust their levels to a nominal +4
V peak-to-peak. The duty cycle of each signal must be adjusted as described in
Section 1.2.
The horizontal drive signal is required to initiate horizontal scan and high
voltage, and should be connected before applying power to the monitor.
3.2
BRIGHTNESS
Normally, the monitor will be used to display alphanumeric or other black
and white information. Moreover, the video polarity is usually white characters
on a black background.
The brightness control should be adjusted at a point where the white raster is
just extinguished. The CRT will then be at its cutoff point, and a maximum
contrast ratio can be obtained when a video signal is applied.
3.3
VIDEO CONTRAST
QlOl is designed to operate linearly when a +2.5 V signal is applied to its base.
Some models incorporate a 500 ohm external contrast control to maintain this
level of +2.5 V peak-to-peak when measured at the video input terminal of the
printed circuit board edge connector. (Refer to the schematic.)
A-6
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