Troubleshooting guide

Cinematronics Vector Monitor Repair Guide v.1.0
Page 7 of 53
R/C Network
The voltage across a resistance-capacitance (“R/C”) network, found at the outputs of the analog
switch IC1, is used to draw screen vectors. The R/C network is responsible for drawing smooth,
straight and precisely positioned vectors. The voltage across the R/C network, at any given time,
determines the actual position of the CRT trace at that time. As the capacitor charges, and the
voltage changes, the CRT trace follows, and the vector is drawn.
Initial position voltages enter from the lower switch channel directly across C101, which charges to
that voltage level rapidly. The voltage is converted to an initial position current by the deflection
amplifiers, positioning the beam at the beginning point of a line segment.
Final position data from the upper switch channel slowly charges C101 through R103 and line
length pot R102. As C101 charges from its initial point value to its final value, a straight horizontal
vector is drawn. Since all this is happening at the same time in the vertical section, a vertical vector
is also being drawn. The combination of both sections moving the CRT beam simultaneously
allows for a vector of any angle to be drawn. Both R/C networks charge simultaneously, which
allows the CRT trace to simultaneously move in the vertical and horizontal direction, so that a
vector can be drawn at any angle.
Pot R102 varies the charge rate of the network, and can lengthen (slower charge) or shorten (faster
charge) the vector for the “on” period of the beam.
R/C NETWORK CIRCUIT