COMPONENT MAINTENANCE MANUAL
IN 1502H RADAR INDICATOR
TM109102
1-32
May/01
excessive, Q4004 will conduct to overcome the positive voltage normally applied to
the base of Q4003. This causes Q4003 to conduct. When it does, C4013 discharges,
ap5 volts to the dead time input of U4001. After C4013 has discharged, the
soft start cycle is repeated. Capacitor C4013 slowly charges to +5 volts again, via
R4013 and operation resumes.
(5) High Voltage Tripler Assembly
Capacitors C4504 through C4509 and diodes CR4503 through CR4508 form a
voltage tripler rectifier circuit that produces a DC voltage approximately three times
the peak ac voltage (7000 volts) across the secondary of T4501. The 21-kV output is
applied to the high voltage anode of the CRT, via P4513, over the shield of a well
insulated cable. The 21 kV high voltage is divided down to a very low level through the
300 megohms in the static convergence assembly and relatively small resistance of
R4502. This voltage sense line is returned to the pulse width modulation control
circuit (U4001) error amplifier input (pin 1) and controls the duty cycle of U4001.
A tap on the secondary of T4501 feeds back the voltage used for the focus adjustment
and grid 2 bias circuits on the high voltage regulator board. The voltage at terminal 4
of T4501 (400 volts peak) is doubled by the rectifier circuit formed by CR4501,
CR4502, C4502 and C4503 to produce 800 volts at the output.
D. Tube Module and CRT Assembly
The CRT connector module is installed on the base of the CRT, providing interface for
all connections to the CRT except anode high voltage. Spark gaps integral to the CRT
socket provide disruptive discharge of electricity to ground for each input. A static
convergence potentiometer is also available.
The horizontal yoke and vertical yoke are installed and aligned at the factory by the
vendor and require no further alignment in the field.
The degaussing coil, L101, is part of the degaussing circuit on the video/RS170
module, and has already been discussed.
The brightness control, R101, is a 1k ohm potentiometer mounted on the front panel
of the indicator. Its operation has also already been explained in the discussion of the
brightness circuit on the video/RS170 module.
E. Low Voltage Power Supply
The low voltage power supply (LVPS) includes an on/off circuit, voltage-controlled
oscillator, resonant circuit, output drivers, output voltage regulator circuit, current limiter,
output transformer, rectifiers and filters. Also included are a monolithic 12 volt regulator
and a precision 2.5-volt reference voltage regulator.'
(1) On/Off Circuit
The document reference is online, please check the correspondence between the online documentation and the printed version.
