Vertical Blanking

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Postwar Television

Vertical Retrace Lines Eliminated

Early Television

Courtesy of Don Patterson

Note: Many sets feed video to the grid of the CRT. In this case, the polarity of the vertical pulse will be wrong, and the circuit shown above won't work. It may be possible to find another point in the vertical scan circuit that provides a negative going pulse. If so, you will have to experiment with the values of R3 and C3.