Keysight N9038A, Service Manual, Page: 242 / 745

242 Keysight N9038A MXE Service Guide
RF Downconverter Section
RF Downconverter Section Troubleshooting
A12 YTF Preselector
There are two different A12 YTF Preselector assemblies used in the N9038A -
one for instruments with Option 503, 508, or 526 and one for instruments with
Option 544.
There are 7 different aspects of the A12 YTF Preselector functionality that can
be verified with the procedures in this section. They are:
1. Assembly Initialization
2. Status LEDs
3. Supply Voltage
4. Tune Voltage
5. Passband Insertion Loss
6. Passband Filter Shape
7. Passband Centering
Due to a lack of access to certain A12 YTF Preselector test points in Option 544
instruments it is not possible to measure all of the control voltages on these
instruments as can be done with the Option 503, 508, and 526 instruments.
However, there are extra LEDs on the Option 544 instruments that can be
monitored. Because of this not all procedures in this section apply to all
instruments.
Assembly Initialization
Before the A12 YTF Preselector assembly will function properly it needs to
initialize itself when the instrument is turned on and be recognized by the
instrument software. To verify that this has happened look at the instrument
Hardware Information screen. To view this information press System , Show ,
Hardware . Once you do this you will see a listing of instrument hardware
assemblies that are installed. The A12 YTF Preselector assembly should
identify itself on this list as YIG Tuned Filter . If this assembly does not identify
itself the cause for this will need to be determined before any other
troubleshooting is performed. The most probable causes for this type of a
problem would be that the A12 YTF Preselector assembly itself is defective,
however, be sure to verify the supply voltage to the assembly before replacing
it.
Instruments with Option 544 also have a series of status LEDs that can be
monitored at instrument boot up to verify that the A12 YTF Preselector is
initializing and working properly. Information on how to interpret these is
covered in the following section.
Since the instrument communicates with the A12 YTF Preselector assembly through the A15
Front End Control assembly, be sure that the A15 Front End Control assembly is initializing
properly before replacing an A12 YTF Preselector assembly for not initializing properly.