If the Frequency Response Test fails by a small amount (5 dB or less), the instrument can probably be fixed by performing the Flatness Adjustment. If an adjustment cannot fix the problem, or the test fails by a large error (5 dB or more), this would indicate a faulty assembly.
In order to troubleshoot an RF problem, refer to the PSA Series Service Guide for troubleshooting procedures and the overall block diagram. Assemblies can be bypassed by injecting 321.4 MHz, or 3921.4 MHz signals at the appropriate places.
If the frequency response test fails at frequencies 3 GHz and above (high bands), the following should be done:
Perform the Frequency Response Adjustment in its entirety. If the adjustment does not fix the problem, or the adjustment can not complete, suspect a hardware problem.
Major assemblies at fault could be:
A19 RYTHM
RYTHM/Bias control signals from the A13 Front End Driver Assembly may be wrong.
The amplitude of the LO signal from A21 SLODA may be too low.
The A10 Third Converter input stage could be damaged.
If the frequency response test fails at frequencies below 3 GHz (Low band), the following should be done:
Perform the Frequency Response Adjustment in its entirety. If the adjustment does not fix the problem, or the adjustment cannot complete, suspect a hardware problem.
Major assemblies to suspect are:
A20 Lowband Assy
optional A22 Lowband preamp
optional A27 Electronic attenuator
A13 Front End Driver circuits that control the assemblies listed
If frequency response fails at several frequencies between 9 kHz and the maximum frequency range of the analyzer (failures in both High band and Low band), and a re-adjustment does not fix the problem, suspect assemblies that are common to both High and Low bands such as a damaged Input Attenuator or the A10 Third Converter.
In order to troubleshoot an RF problem, refer to the PSA Series Service Guide for troubleshooting procedures and the overall block diagram. Assemblies can be bypassed by injecting 321.4 MHz or 3921.4 MHz signals at the appropriate places.
If the Option B7J Frequency Response test fails, but the standard frequency response is in spec, suspect the A27 Electronic Attenuator or A27 interconnect cables. If both the Option B7J and the standard frequency response fail, troubleshoot as if B7J were not present, but do not discount the signal path switch in the A27 electronic attenuator.
Option 123 places a dual mixer parallel to the A19 RHYTHM. If the Option 123 Frequency Response test fails, and the Frequency Response Adjustment (Option 123) does not fix the problem, then try performing the Switched LO Distribution Amplifier (SLODA) Adjustment and re-running the Frequency Response (Option 123) Adjustment. If this doesn't fix the problem, then either the dual mixer, the bypass switches, or the A21 SLODA could be defective.