Preselector Tune Output - Keysight n9020a Service Manual

Front End Control Troubleshooting
A15 Front End Control Assembly Troubleshooting

Preselector Tune Output

The Presel Tune connector A15J300 (FEC) or A15J302 (EFEC) is a test point
used to verify the internal A12, YIG Tuned Filter drive voltage variations with
center frequency. The YTF is used in the high band path (3.6 GHz to the
analyzer's maximum frequency). Connect Presel Tune to a voltmeter. Use the
MMCX (m) to SMB (f) to connect to Presel Tune on the A15 board and
appropriate adaptors to connect to the voltmeter. Refer to
5-2
adapter, part number E9637A for the Voltmeter. The preselector tune output
voltage can be measured to verify this portion of the A15 is functioning.
Press System, Alignments, Auto Align, Off on the analyzer once it has fully
booted to the spectrum analyzer application. Press Span, Zero Span on the
analyzer. The preselector tune output voltage in high band should change
when the center frequency of the analyzer is changed.
Preselector tune output measurements are not valid for Option 503, 3 GHz
NOTE
frequency range.
Table 5-8 Preselector Tune Output Voltages
Center Frequency
(GHz)
5.0
10.0
15.0
20.0
26.0
Even if the voltages listed in the table are correct it does not guarantee the
proper control current is getting to the YTF. There is not a convenient way to
measure the control current, so if a high band issue is suspect it is
recommended that the A15 is changed out first before changing the YTF since
the A15 board has easy access.
To further test the YTF control current, select Amps on the DVM and place the
positive lead of the DVM on one of the YTF Coil Current P8 pins and the other
DVM lead to the other Coil Current pin.
In order to measure the control current correctly, press Single on the analyzer
NOTE
in between each measurement.
or Presel Tune location. You may also need a Banana plug to BNC (f)
~ Tune Vol tage
(VDC)
1.6
3.3
4.85
6.5
8.45
Valid Frequency
Range Option
508, 513, 526
513, 526
526
526
526
218
Figure 5-1 or Figure