Wells-Gardner Electronics Corporation

Q317, Q318 are off when horizontal frequency is 53KHz α 61KHz

Q316, Q317, Q318 is off when horizontal frequency is 62KHz α70KHz

8-6 FBT (Flyback Transformer):

The high voltage for CRT anode focus, G2 voltage for CRT and – 12V for vertical deflection are generated by the FBT. Also, -130V for G1 voltage, horizontal flyback pulse, +128V video supply, and for dual focus units 800V dynamic focus supply.

8-7 ABL (Automatic Beam Limiting):

The voltage of point 7 depends on the anode current of FBT. So, the voltage at pin 7 of the FBT decreases with increasing anode current. That time, using at this level, increase contrast setting level limited a certain level (32FtL in white pattern) that is set by inner voltage of IC401.

8-8 Video amplification section:

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.