Service manual

STP 11-25R13-SM-TG
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Performance Measures Results
1. Review DA Form 2407. P F
2. Sectionalize the trouble to a defective stage. P F
a. Visually inspect for discrepancies. P F
b. Clean the exterior and CRT. P F
c. Operations check. P F
3. Localize the trouble to a specific circuit. P F
a. For intermittent changes in color, brightness, size, or position, check for bad
connections.
P F
b. Ghosting, shadows, or streaks next to vertical edges in the picture indicate
problems with input signal termination.
P F
c. For color blotching or other color and distortion problems, locate and eliminate
sources of magnetic fields and degauss the CRT.
P F
d. No sound or raster are symptoms caused by a short in the low voltage power
supply.
P F
e. Common causes of blooming are a weak high voltage rectifier to too little bias on
the CRT.
P F
f. If the picture screen is dark but the sound is normal, check the H output. P F
g. For no synchronization, check the H and V deflection oscillator. P F
h. A black screen with power ON indicates that both the H and V syncs are missing;
check the sync separator circuit.
P F
i. Symptoms of the H oscillator not oscillating are no drive signal to the H output
circuit, no high voltage or boost voltage, and a dark picture screen.
P F
j. Identify sweep circuit problems. P F
k. A horizontal line indicates a vertical problem. P F
l. A weak picture or snow indicates video amplifier stage problems. P F
m. For picture pulling, weak brightness modulation, bending, or washout, check the
AGC circuit.
P F
4. Isolate the fault to a component. P F
a. For problems in the low voltage power supply, measure DC voltage on each
branch.
P F
b. With power OFF and the power cord unplugged, check resistance of
semiconductors in the power supply for short circuits with a multimeter.
P F
c. For thermal or warm-up problems, use a can of cold spray and a heat gun. P F
d. Troubleshoot the H output circuit. P F
e. Measure the waveforms at all outputs and inputs of the H oscillator and related
circuits.
P F
f. Troubleshoot marginal failure of sweep circuit. P F
g. Troubleshoot video circuit problems. P F
5. Replace, repair, or adjust faulty component. P F
a. Perform preliminary procedures before proceeding with adjustments. P F
b. Adjust color purity. P F
c. Adjust H and V CENTERING. P F
d. Adjust H and V SIZE. P F
e. Adjust convergence. P F
f. Adjust screen bias with color bars from the VTSG. P F
g. Adjust final settings for SCREEN BIAS. P F
h. Adjust RGB SCREEN GAINS. P F
i. Turn OFF the receiver/monitor and replace the back cover. P F
6. Operations check. P F
a. Check that the power switch turns ON and OFF. P F
b. Check the operation of the volume control. P F