Speco Technologies VM-1201 service manual Video input block, Vertical & horizontal processor

•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.

2.2Video 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.

2.3Vertical & 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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