COMPONENT MAINTENANCE MANUAL
IN 1502H RADAR INDICATOR
TM109102
1-14
May/01
The sawtooth is terminated by the leading edge of the Y-retrace pulse and the sawtooth
for the next vertical sweep is triggered by the trailing edge of the Y-retrace pulse.
During trace time, the circuit operates from +/-12 volts. During retrace, the +52 volt supply
is used to allow the beam to retrace in the allocated time.
Various controls are provided in the vertical sweep circuit to accommodate the radar,
CCIR, and RS-170 video inputs that might be used. One set of controls (VERTICAL
SIZE) determines the height of the display. The settings of the other set of controls
(VERTICAL POSITION) determine where the display begins at the top of the screen.
C. High-Voltage Supply
The high-voltage supply consists of the high-voltage regulator module and the
high-voltage block assembly. It supplies 21 kV, regulated to +/-1%, to the anode of the
CRT. It also supplies adjustable DC outputs for focus (grid 4) and for G2 bias.
As mentioned earlier, the high voltage supply is enabled by the +27 volt sweep reference
signal from the horizontal sweep circuit. The sweep reference signal is applied to the high
voltage on/off circuit. If the sweep reference input is absent, the high voltage supply shuts
down, preventing possible CRT damage.
The driver is a transistor that is switched on and off at a controlled rate to supply 28-volt
pulses to the primary of a transformer in the high voltage block assembly. The duty cycle
of the driver output is controlled by the pulse-width modulation (PWM) control circuit. The
X-retrace input controls the PWM frequency. The output from the secondary of the
transformer is fed to a high voltage tripler, which supplies the 21 kV anode voltage to the
CRT.
A tap on the secondary of the transformer picks off 800 volts, which is rectified and fed
back to focus and bias circuits. Both of these outputs are routed to the tube module. The
adjustable focus voltage is connected to grid 4 and the adjustable bias voltage is
connected to grid 2.
The horizontal static convergence circuit is located in the CRT connector module. The
high voltage output from this circuit is adjusted to provide convergence at the center of the
screen.
D. CRT Connector Module
The CRT connector module is installed on the base of the CRT. It provides the interface
for all connections to the CRT except anode high voltage. The video is applied to the
three cathodes, or color guns. Filament voltage comes from the low voltage power supply.
E. Low-Voltage Power Supply
The low-voltage power supply (LVPS) provides the DC operating voltages for the indicator
circuits. The power supply operates from the aircraft 28 Vdc source, which is always
connected to the input. The LVPS is turned on and off by an input from the on/off circuit
on the video/RS-170 module.
The document reference is online, please check the correspondence between the online documentation and the printed version.
