Service manual

STP 11-25R13-SM-TG
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Performance Measures Results
NOTE: An out-of-phase source displays color loss or shifting hue when switching between
sources. Even though all signals lock to the house reference, timing errors arise as signals
travel through different cable lengths. Therefore, adjusting timing delay for each piece of
equipment brings all signals into synchronization at the switcher. If unattainable on the
equipment adjustments, use delay lines and cable length to correct timing and phasing
errors. Cut cabling to match the longest cable run. Using the 66 percent propagation factor,
1 degree of phase is equal to 6.035 inches and 1 nsec of timing is equal to 7.778 inches.
6. When checking VTRs, PLAY a videotape with prerecorded color bars. P F
NOTE: Since VTR transports produce wow and flutter (jitter or instability) at their outputs,
VTRs include time-base correctors (TBCs) to eliminate jitter and compensate for timing
variations in the playback signal.
a. Observe the Black level on the WFM and adjust TBC SETUP to 7.5 IRE.
Adjusting SETUP alters the apparent brightness of the image on the monitors.
P F
b. Observe the White level on the WFM and adjust TBC VIDEO to 100 IRE.
Adjusting VIDEO alters the apparent contrast of the image on the monitors.
P F
c. Observe the color bar pattern on the vectorscope and adjust TBC HUE PHASE to
align the burst vector dot with the 75-percent/100 percent mark. The other vector
dots that represent the various colors should line up with, though possibly not
within, their respective boxes.
P F
NOTE: Yellow (YL) = 167 degrees; Red (R) = 104 degrees; Magenta (MG) = 61 degrees;
Blue (B) = 347 degrees; Cyan (CY) = 284 degrees; and Green (G) = 241 degrees.
d. Observe the Chrominance display on the WFM and adjust TBC HUE GAIN to
modulate the Chrominance signals at their proper levels. On the vectorscope, if
some vector dots center in their boxes but other do not, compromise the setting.
P F
7. Place color bars on all sources and check each individual piece of equipment to meet
EIA RS170A specifications.
P F
a. Vertical blanking interval (VBI): 1.17 to 1.33 msec or 21 lines. P F
b. H and V blanking: 10.49 to 11.44 usec. P F
c. Pulse width: 2.54 usec. P F
d. SC frequency: 3.579545 MHz +/- 10 Hz. P F
e. Sync level: 40 IRE. P F
f. Video level: 100 IRE. P F
g. Setup: 7.5 IRE. P F
h. Burst level: 40 IRE. P F
i. Chroma level: 80 IRE on WFM and within vector boxes on the vectorscope. P F
j. V sync pulse: 3H. P F
k. H sync pulse: 4.45 to 5.08 usec. P F
8. Check SC/H phase. P F
a. Zero SC/H phase is the coincidence of the zero crossing of SC the same phase as
color burst with the 50 percent point of the leading edge of H sync.
P F
b. Color frame one is equal to SC zero crossing negative going on the odd-numbered
lines.
P F
Evaluation Guidance: Score the soldier a GO if all steps are passed (P). Score the soldier a NO-GO if
any step is failed (F). If the soldier fails any step, show what was done wrong and how to do it correctly.
Have the soldier practice until he can correctly perform the task.
References
Required Related
Mfg Manuals NTSC Studio Timing (GVG)
Prof Video Tutorial (GVG)