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A3 Assembly Video Circuits
Voltages from
to the A3 Variable Gain Amplifier correspond (approximately)
to on-screen signal levels. (One volt corresponds to the top of the screen and zero volts
corresponds to the bottom of the screen.) This is true for both log and linear settings except
when the spectrum analyzer is in 1 dB/div or 2
In these cases the log expand
amplifier is selected, and 1 V corresponds to top-screen and 0.8 or 0.9 V corresponds to
bottom-screen. The spectrum analyzer can be set to zero span at the peak of a signal to
generate a constant dc voltage in the video circuits during sweeps.
1. Disconnect W26 from
and
from
2. Connect W26 to
3. Set the spectrum analyzer to the following settings:
Span . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Sweep time
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20ms
Resolution bandwidth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 MHz
Log/division
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 dB/DIV
4. If a trace is displayed, troubleshoot the A3 assembly. If a trace is absent, connect an
oscilloscope to the rear-panel BLKG/GATE OUTPUT.
5. The presence of a TTL signal (TTL low during 20 ms sweep) indicates a good A3
Interface Assembly. Troubleshoot the IF section.
6. If the BLKG/GATE OUTPUT is always at a TTL high or low, troubleshoot the A3
trigger/video gating circuits.
7. Reconnect W26 to
and
to
8. Remove the A3 assembly shield.
9. If the video filters appear to be faulty, refer to “Video Filter” in this chapter.
10. If there appears to be a peak detector problem, refer to “Positive/Negative Peak
Detectors” in this chapter.
11. Connect the spectrum analyzer CAL OUTPUT to the INPUT
and set the controls as
follows:
Center frequency
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Span . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Reference level
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -10
12. If the spectrum analyzer works correctly in 5 dB/div and 10 dB/div but not in 1 dB/div
or 2
refer to “Log Offset/Log Expand” in this chapter. Continue with step 13 if
the problem involves on-screen amplitude errors which appear to originate in the video
chain.
13. Press
and
IF AD3 ON OFF
until OFF is underlined. Monitor
with an
oscilloscope. If the voltage is not approximately
Vdc, troubleshoot the Log Amplifier
on A4. (Refer to the IF troubleshooting procedure in Chapter 9, “IF Section.“)
14. To confirm proper video input to the video circuit, set the spectrum analyzer to Log
10
per division and change the reference level in 10
steps from -10
to
j-30
At each 10
step, the input voltage should change 100
The input level
should be
Vdc for a j-30
reference level.
8-14
Section
Содержание 8562E
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Страница 158: ...A9 Input Attenuator 9 c 9 d 1 slll3e Figure 4 15 A9 Mounting Screw at Right Side Frame Assembly Replacement 4 33 ...
Страница 172: ...Procedure 13 Rear Frame Rear Dress Panel Figure 4 23 A6 Power Supply Cover SP14E Assembly Replacement 4 47 ...
Страница 204: ...I _I 8560E Series I I sl134e F i g u r e 5 2 P a r t s I d e n t i f i c a t i o n C o v e r A s s e m b l y I I ...
Страница 205: ...8560E Series sl131e FIGURE 5 3 PARTS IDENTIFICATION MAIN CHASSIS v ...
Страница 207: ...8 5 6 2 E sl128e 12 9 p3 CES F i g u r e 5 5 P a r t s I d e n t i f i c a t i o n F r o n t F r a m e ...
Страница 213: ...w51 W2 W52 N5A A4 _ w 5 5 w27 Figure 6 3 Top View A2 and A3 Unfolded S K 1 5 7 Major Assembly and Cable Locations 6 5 ...
Страница 217: ...w20 C O A X 6 w 7 w 5 9 C O A X a 3 9 sj138e Figure 6 7 Al6 Fast ADC Option 007 Major Assembly and Cable Locations 6 9 ...
Страница 219: ...FL 4 Bl Figure 6 9 Rear View BTl A20 SK162 Major Assembly and Cable Locations 6 l1 ...
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