Troubleshooting guide

Cinematronics Vector Monitor Repair Guide v.1.0
Page 14 of 53
High Voltage Oscillator (early discrete monitor only)
The HV Oscillator only appears in the discrete HV Cinematronics monitors (all monitors prior to
Rev.G). This circuit is incorporated into the Keltron HV box for later monitors. The integral
elements of the HV oscillator section are IC9, IC5, Q4 and flyback transformer T1. The +/-18V
regulators IC9 and IC5 deliver +36 volts across C18. The frequency of oscillation is dependant on
the winding characteristics of the HV Transformer, T1. As current begins to flow through pin 4 of
T1, a reverse potential is induced in the thicker coil at pins 1 and 2, tending to shut off Q4. Q4 turns
on again after the R14/C19 time constant discharges, repeating the cycle. The tank circuit of D8,
R15 and C20 provide a protective sink circuit against inductive spikes that must otherwise cripple
TIP51C. Diode D7 protects against reverse currents.
The secondary windings of T1 generate an 800-volt peak-to-peak waveform at pin 7 that is half
wave rectified by D10 and filtered by C22 to provide +400 volts DC of focus control.
Beam cutoff voltage (+90 volts DC) is supplied by a 200-volt peak-to-peak signal on pin 8,
rectified by D6 and filtered by C17.
[insert scan from Rip Off manual]
Voltages
There are several voltage regulators in the monitor: +18V, +15V, -18V, -15V. These are fed by a
+25V and a -25V source. If one or more of these voltages were incorrect, that would easily cause
deflection problems. The +18V (7818) and –18V (7918) regulators can be replaced with +/-15V
regulators. A detailed discussion is included in the Factory Service Upgrade section of this
document.