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Front End Control Troubleshooting
A15 Front End Control Assembly Troubleshooting
If any of the preselector control currents do not match the levels shown in
Figure 5-9, the most probable causes are a misaligned YTF or the A15 Front
End Control Assembly. Perform the YTF characterization (press System,
Alignments, More, Ad vanced, Characterize Preselector) and re-check the
control current at various center frequencies.
NOTE Tolerances should be used as a guideline. The true test is whether or not the
analyzer will function and meet published specification.
Front End Assembly Control Logic Verification
Since the RF Front End Troubleshooting board is connected, now is a good
time to test out the remaining control circuits from the A15 Front End Control
Assembly.
Table 5-9 YTF Tune Current
Center Frequency
(GHz)
Control Current
(ma)
Tolerance
(ma)
5.0 106 ± 20
10 215 ± 25
15 324 ± 30
20 430 ± 40
26 560 ± 50
Table 5-10 Front End Control Logic
Test Point Description Instrument
Settings
Voltage
(VDC)
Tolerance
(VDC)
S2A Sets switch for Low Band/preamp path CF 50 MHz preamp
on
+9.67 ±0.5
S2B Sets switch for Low Band/preamp path CF 50 MHz preamp
on
+9.83 ±0.5
S3A Sets E-atten to 5 dB preamps off E-atten = 5 dB +9.67 ±0.5
S3B Sets E-atten to 5 dB preamps off E-atten = 5 dB +9.83 ±0.5
S4A Sets E-atten to 10 dB preamps off E-atten = 10 dB +9.67 ±0.5
S4B Sets E-atten to 10 dB preamps off E-atten = 10 dB +9.83 ±0.5
S5A Sets E-atten to 2 dB preamps off E-atten = 2 dB +9.67 ±0.5
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