akira 21BHS3/CE, Service Manual

Page: 7 / 24

7
Model No: 21BHS3CE
Version 1.0
HORIZONTAL AND VERTICAL CIRCUIT
Through Synchronous separating circuit, the video signal is divided into horizontal-Synchronizing
signal and Vertical-Synchronizing signal. The horizontal-Sync pulse coming from pin 33 is transferred
to the horizontal-drive transistor.
The cathode driving voltage 180V vertical drive v15V and –15V are all generated from
FBT.
The vertical sawtooth waveform is generated on the pin 21 and 22, and then enters the vertical
amplifier STV9302A. STV9302A is a 7 pins vertical deflection circuit (2 Amperes) for DC-coupled
90° or 110° deflection systems with frame frequencies from 50 up to 120 Hz. one supply voltage for
the scanning and second voltage supply for the flyback are needed.
The vertical drive currents of OM8370 pins 21 and 22 are connected to input pins 1 and 7 of
STV9302A. The vertical scanning output is coming from pin 5 and feed back to pin 1 by R405. The
supply voltage is
± 15V at pin 2 and pin 4. C406 is the pump capacitor.
Power supply
The IC of KA5Q0765RT is adapted in this chassis; it is the product of Fairchild. It supplies four DC
voltages, one is the +B
＝ 110V, another is Hcc ＝ 26V, the third is 13V (the sound drive voltage), the
fourth is +16V. The +16V can generate the +8V, +5V and +3.3V by the special generators.