Table of Contents
Advertisement
SECTION 16
HIGH VOLTAGE POWER SUPPLY (A10)
16-1. GENERAL.
CRT bias and drive voltages are provided by the high voltage power supply. The power
supply converts a nominal15 VDC input to output voltages of +4kVand a-2 kV.In addition, control circuits for
the CRT focus and intensity grids are contained in this power supply. The high voltage power supply block and
schematic diagrams are shown in figures 16-1 and 16-2, respectively.
16-2. HIGH VOLTAGE SUPPLY. An 8 VDC at the center tap of the high voltage transformer is switched,
through the transformer primary winding by the chopper, at a 20kHz rate. The chopper drive signals originate
in the low voltage power supply. One transformer secondary winding provides a 6.3 VAC CRT heater voltage.
The other transformer secondary winding provides a 1 kV to a X4 multiplier and a X2 multiplier. The output of
the X4 multiplier, a nominal +4 kV is the CRT anode voltage. A nominal -2 kV output of the X2 multiplier is
applied to the intensity and focus modulators. The -2 kV is regulated by comparing a sample of the -2 kV to
a
6.3V reference signal. The resultant signal controls the level of the DC input at the center tap of the high voltage
transformer. A bias divider, on the transformer center tap, provides the HV CHOPPER BIAS signal to the low
voltage power supply.
16-3.
INTENSITY AND FOCUS CONTROL.
An 87V zener diode and a resistive divider circuit provide the
intensity and focus voltages. Each modulator provides variable output voltages, within their bias range, under
the control of the low voltage INTENSITY TV and FOCUS TV input signals. The grid and focus voltages are
stabilized by using DC control loops. The INTENSITY SAMPLE signal and the HV REF signal are compared, on
the scope amplifier module, to an input control signal. The result of this comparison is the INTENSITY TV
signal. In a similar manner, the FOCUS SAMPLE signal is compared, on the scope amplifier module, to the
input control signal. This results in the FOCUS TV signal.
16-1
Advertisement
Table of Contents
