Keysight Technologies N5247B Service Manual page 133

Troubleshooting
Measurement System Troubleshooting
Checking the A14 50 MHz Reference Outputs
1. Refer to the block diagram at the end of this chapter and to
All Cables—All Options, S/N Prefixes <6021" on page
cables W75, W76, and W77, at the A14 frequency reference board.
2. Disconnect cables W75, W76, and W77, one at a time, from the A14
board.
3. Connect the spectrum analyzer to the open connector on the A14 board.
4. The spectrum analyzer should measure a signal at 50 MHz.
5. If any of the 50 MHz signals are not present, replace the A14 frequency
reference board. Refer to
on page
6. If the 50 MHz signals are present, reconnect the cables, and then:
— for LO related problems, continue testing at
— for source related problems, continue testing at
Checking the A15 Direct Digital Synthesizer (DDS) Assembly Outputs
The instrument must be sufficiently reassembled, so it can be safely powered
up.
1. Power up the instrument.
2. Note any error messages in the bottom right hand corner of the PNA's
display (e.g., "A power on self test error has occurred.
Please contact..."). Refer to
3. A log file is generated by PNA after every power up. To access this log file,
on the PNA, navigate to E:/log/PowerOnTest (Verify that hidden files is
selected). A failure indication similar to "FAIL: Slug S/N not found",
indicates the DDS assembly is faulty, for an example of this error in a log
file, refer to
4. If an DDS failure (e.g., "FAIL: Slug...") is observed:
a. Power down the instrument.
b. Verify that the A15 DDS assembly is seated properly.
1. A14 frequency reference board only applies to instruments with serial number pre-
fixes <6021.
2. The A15 direct digital synthesizer assembly only applies to PNAs with serial number
prefixes ≥6021 or
Keysight N5247B Service Guide
"Removing and Replacing the A4–A17 Boards"
7-18.
GHz LO Synthesizer Output".
and A17 Source Synthesizer Outputs" on page
Figure 4-11 on page
that has been
1
"Checking the A15 13.5
Figure 4-10 on page
4-39.
upgraded with a version 7 synthesizer assembly.
"Top Cables,
6-21. Locate flexible
"Checking the A4
4-43.
2
4-38.
4-37