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Service Adjustments (Electronic Controls, cont.)
Clock Adjustment (Sb)
Preparation:
Connect the frequency counter from TPS1 (IC001
Pin 13) to cold ground (
).
Note: Frequency Counter probe capacitance should
be 8pF or less.
Procedure:
1.
Turn the Receiver “OFF” with the AC
power applied.
2.
Measure TPS1 (IC001 pin 13) for the frequency of
the waveform and record the reading.
Note: Pin 13 measurement must have at least four
digits of resolution following the decimal point.
Example: 000.0000
3.
Turn the Receiver back “ON”.
4.
Place the Receiver into Serviceman Mode for
making electronic adjustment, select the Clock
Adjustment DAC (Sb).
5.
Calculate and set Sb based on the
following formula:
Note: Pin 13 measurement will not change
regardless of the value stored in Sb.
Vertical Size (B7)
1.
Adjust the VERTICAL SIZE DAC control, B7, until
the top and the bottom edges of the raster are
visible.
2.
Adjust the VERTICAL SIZE control, B7, until the
top and the bottom of the raster touch the bezel
edge. The advance SIZE control to obtain an
approximately 10% overscan. Linearity adjustment
is don automatically when the size is being
adjusted. (Best results can de obtained with a
round test patter.)
Service Adjustments (Mechanical Controls)
VCO Field Alignment L105
(IC101 pins 35 & 36)
1. Connect a balance antenna and select a midband
channel (Ch 10, 11 or 12)
2.
Attenuate the signal strength for a weak noisy
video.
3.
While observing the picture tube, adjust L105 until
best picture appears.
4.
Change channels and observe that they are tuning
properly.
5.
If the channel monitored is not clear, repeat steps
1, 3 and 4 while applying a stronger signal.
Focus (T551)
Preparation:
Connect a Signal generator and select a dot pattern.
Procedure:
Adjust the FOCUS control to obtain the sharpest and
clearest dot pattern.
a. Adjust for best center.
b. Adjust for best area between the center and top
right corner.
Sb
128
0.901
6
×
10
244.1406
pin13 Hz
[
]
–
{
}
244.1406
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