IIYAMA A705MT
Instrukcja Serwisowa

4-7. CONTROL circuits
(1) HORIZONTAL / VERTICAL OSCILLATION circuit The sync signal input to IC301 is phase-sifted and converted to the waveform in IC301. The pulse synchronized with the horizontal sync signal is output from pin 17 as horizontal drive pulse. The sawtooth wave synchronized with the vertical sync signal is output from pin 4. The pulse output from pin 17 generates a frequency locked to the input signal under the following conditions:

Q The horizontal sync signal is input to pin 26. R The vertical sync signal is input to pin 27. S The feedback pulse (AFC pulse) of the HORIZONTAL DEFLECTION OUTPUT circuit is input to pin 18.
IC301 is auto-sync system and adjusts the horizontal frequency automatically make the vertical sync signal input to pin 27 trigger. In case that the AFC pulse is not input, the output pulse from pin 17 is unlocked and the horizontal picture size changes with keeping it small.

IC301 pin 26: Horizontal sync signal input

IC301 pin 17: H-DRIVE pulse output

IC301 pin 18: AFC pulse input (Threshold level: approx. 2V)

Center voltage: 3.5V

IC301 pin 4: V-sawtooth wave output

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