Service manual

STP 11-25R13-SM-TG
3 - 28
REPAIR A TELEVISION RECEIVER/MONITOR
113-575-0051
Conditions: In a tactical or garrison environment, given an inoperable or malfunctioning TV receiver or
monitor with an accompanying DA Form 2407, sync generator, VTSG, dual-trace oscilloscope with 10X
test probes, multimeter with test leads, isolation transformer, degaussing coil, 75-ohm coaxial video cable
with BNC connectors, 75-ohm terminators, mirror (larger than the size of the screen), reference light
source, electronic equipment tool kit, soldering tool kit (light to medium duty), heat gun, cold spray, clean
cloth, glass cleaner, bench stock, cellophane tape, manufacturers' manuals, and DA Pam 738-750.
Standards: The standards are met when the repaired TV receiver or monitor has even purity across the
entire screen and the convergence pattern is centered on the screen with pure white dots or
crosshatches.
Performance Steps
1. Review DA Form 2407.
2. Sectionalize the trouble to a defective stage.
a. Visually inspect for physical damage, missing controls, broken switches, burned out
components, and other discrepancies.
b. Clean the exterior and cathode-ray tube (CRT) face with a clean cloth and glass cleaner.
c. Operations check to verify that the deficiency or symptom exists and to what extent.
(1) Connect and turn ON the VTSG, sync generator, and receiver or monitor.
(2) Select EXT on the SYNC selector switch to lock the monitor to the external sync source
from the sync generator.
(3) Select the VTSG EIA color bars signal.
(4) Press the degauss pushbutton for at least five seconds.
(5) Verify the video input and analysis the picture on the screen.
(6) Check all front-panel controls for proper setup and range of operation.
( a) Check the mode selector switch for color presentation in the AUTO and COLOR
positions. Check for a black and white picture in the monochrome (MONO) position;
then return the switch to AUTO.
( b) Rotate the BRIGHTNESS control fully clockwise (CW) and observe the change in
picture brightness. Return control to the preset position.
( c) Rotate the CONTRAST control fully CW and observe the change in picture contrast.
Return control to the preset position.
( d) Rotate the CHROMA control fully CW and observe the change in Chroma saturation.
Return the control to the preset position.
( e) Rotate the HUE control fully CW and observe the changing phase of the color bar
signal. Return the control to the preset position.
( f) Rotate the APERTURE control fully CW to observe a variable change of mid-
frequency boost in picture luminance. Return the control to the preset position.
(7) Recognize symptoms (picture, sound, and raster).
3. Localize the trouble to a specific circuit by analyzing overall block diagrams and by performing
functional tests on suspected circuits.
a. For intermittent changes in color, brightness, size, or position, check for bad connections inside
the receiver/monitor or at cable connections.
b. Ghosting, shadows, or streaks next to vertical edges in the picture indicate problems with input
signal termination (impedance), including the use of cable extensions, excessively long cables,
cheap or improperly made video cables, improper looping of equipment and monitors, or
problems in the video source or receiver/monitor circuitry.
c. For color blotching or other color and distortion problems, locate and eliminate sources of
magnetic fields and degauss the CRT.
d. No sound or raster are symptoms caused by a short in the low voltage power supply.