Speco Technologies VM-1201 - Manual (Page 9)

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Snubber circuit ：Snubber C907, D902, R902.
Primary side self-powering circuit ：D903,C914.
Output 13.5 volts for vertical & horizontal drive circuits ：D904, C915.
Output 27.5volts for horizontal deflection circuit ：D906 ,C916.
2.2 Video input block
Signal input buffering and switch
‧ CVBS Input buffer ：Q201 & R201,R202.
Video filter & output stage.
‧ Video input：Through C202 to W202 (Contrast VR ) and differential amplifier Q202,
Q203.
‧ Video amplifier: Cascade amplifier R219, Q204, Q205, R222, C206.
‧ Brightness control:VR201, R214, R225, R226, Q204.
2.3 Vertical & horizontal processor
2.3.1 Vertical guard:
This vertical feedback signal on pin2 when the level on pin 2 is below 0.35v or high
than 1.85v the guide circuit inserts a continuous level of 2.5V in the sandcastle output
signal of pin 17.The results in the blanking of the picture displayed, thus preventing a
burnt-in horizontal line.
2.3.2 Vertical drive output:
The drive o/p pin1 of U401 delivers a drive current of 1.5mA at 5V output through R302
to U402 pin1.
2.3.3 Sync separator:
The video input through C401, R401 and filter C402 to pin 5 of U401.The Sync separator
is designed such that the slicing level is independent of the amplitude of the Sync pulse. The
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