Wells-Gardner D9100 - Manual (Page 19)

8-8.1. Video pre-amplifier(IC401).
Input video signals are amplified by means of IC401, and the amplified signals
drive the video output stage (IC402). Video gain is adjusted by DC voltage at
pin 12 for ABL control.
8-8.2. Video output stage (IC402).
The video output signals from IC401 are amplified again by IC402, and IC402
applies video signals to each cathode of the CRT. Cutoff voltages are adjusted
by Q405, Q406, and Q407 which is operated by I²C BUS control through the
microprocessor.
8-8.3. OSD (On Screen Display : IC403).
The OSD signal is applied from IC403 to IC402. It is controlled by I²C BUS
control line.
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