Sencore PS163 - SETTING THE TINT RANGE WITH THE VECTOR PATTERN; ADJUSTING the 3.58 MHz OSCILLATOR; ALIGNING THE BANDPASS AMPLIFIER; TROUBLESHOOTING WITH THE VECTOR PATTERN

SETTING THE TINT RANGE WITH
THE VECTOR PATTERN
The tint range may be adjusted, with the vector pat-
tern, to provide the proper flesh tone at the mechnical
center of the control. Rotate the tint control and note
that the pattern will also rotate on the scope screen.
The tint control should be centered and the burst
phase adjusted so the third or R-Y bar points straight
up at the R-Y mark on the vector graticule. Rotate
the tint control to each end. The third bar should
move at least one mark on the vector graticule, or 30
degrees either side of its proper position. If the tint
control is to one side of its rotation when the R-Y
bar is in its proper position, there will not be enough
tint range to insure proper flesh tones on all stations.
Set the tint control to its mechanical center of its
rotation. Rotate the tint control to each end. The
third bar should move at least one mark on the vector
graticule, or 30 degrees either side of its proper po-
sition.
ADJUSTING the 3.58 MHz
OSCILLATOR
The vector pattern can be used to set the 3.58MHz
color oscillator to its exact frequency. First, the
reactance test point or other test point as indicated in
the manufacturers service literature must be shorted
out. There will be a barber pole effect on the re-
ceiver screen and the vector pattern will appear to be
rotating. Adjust the 3.58 oscillator transformer or
coil until the pattern stops, or is rotating the slowest.
This is the correct setting of the 3.58MHz oscillator.
Remove the short and check for proper color on the
receiver screen.
ALIGNING THE BANDPASS
AMPLIFIER
The vector pattern and its important points are all
you need to align the bandpass amplifier in most
color television receivers. Use the following procedure,
along with the four important points of the vector
pattern, to align tube or solid state bandpass am-
plifiers.
1. Adjust the chroma bandpass transformer for the
best shape and amplitude of the vector pattern. The
most common system is the single bandpass trans-
former with two adjustment slugs. Normally, the bot-
tom slug is adjusted for the straightest sides down to
20
the center of the pattern. The top slug for straight
sides and maximum amplitude. (Be sure that the
color level control on the receiver is set to about mid
point here. An excess of color signal can overload the
amplifier and distort the pattern making alignment
impossible).
2. Adjust the chroma takeoff coil for maximum am-
plitude with no distortion and straight sides of the
petals. (Be sure to observe all the bars in the pattern,
when making all of these adjustments, to be sure you
are not increasing some while decreasing others.
Fig. 13. Vector pattern showing incorrect
4.5MHz trap adjustment. 4
If the pattern appears fuzzy, as in Fig. 13, check the
alignment of the 4.5MHz trap. Misalignment of this
trap will cause the pattern to appear as shown and also
cause sound interference in the color when the re-
ceiver is tuned to a station signal.
TROUBLESHOOTING WITH THE
VECTOR PATTERN
Defects in the color circuits of any color receiver can
be isolated by using the vector pattern and the dual
trace 25163. Here are a few of the more common
troubles and how they will appear on the vector scope;
Weak or Loss of Red: The photo in Fig. 14 indicates
a weak R-Y signal. The vertical amplitude of the
vector pattern is low, and the pattern appears squeezed
in the vertical direction. Note that the blue or B-Y
signal appears to have the correct amplitude of signal.
Here, a check of the R-Y difference amplifier and the
demodulator circuits should locate the problem.
Weak or Loss of Blue: A weak blue or B-Y signal is in-
dicated by a pattern that is narrow horizontally as
shown in Fig. 15. A check of the B-Y difference
amplifier and the demodulator stage should locate the
problem. You can use the 25163 front panel vector
inputs to display the vector pattern at the output of