294 Keysight N9038A MXE Service Guide
Front End Control
A15 Front End Control Assembly Troubleshooting
The value for each of the power supply LEDs is shown in Table 8-9.
8. Verify that the serial communication interface for the A13 RF Front End
assembly identification on the A15 Front End Control assembly is working
properly by pressing System, Show, Hardware.
If there is a Front End entry on the Hardware Information screen proceed
to the next step. If not, there is most likely a problem with the A15 Front
End Control assembly.
9. Tune the instrument to a frequency of 50 MHz with a span of 0 Hz by
pressing FREQ, 50 MHz and SPAN, Zero Span.
10.Turn off the RF Preselector by pressing Input/Output, RF Input, RF
Preselector Off.
11.Measure the voltage level of the Test Points listed in Table 8-10 for the
Internal Preamp Off condition.
If the test point voltages are correct (±0.5V) proceed to the next step. If
not, there is most likely a problem with the A15 Front End Control
assembly.
Table 8-9 A13 RF Front End Assembly Front End Test Board LEDs
LED Power Supply Voltage
DS1 −15V
DS2 +5.2V
DS3 +15V
DS4 +9V
The Front End Control Test board has the circuitry on it to simulate the presence of an A13 RF
Front End assembly. When the instrument is booted up with the test board connected it will
return, via the serial communications interface, similar information to an actual A13 RF Front
End assembly. This information can then be viewed on the instrument Hardware Information
screen.
If neither the A11 RF Switch / High Band Preamp assembly nor the Front End Test board is
connected to the A15 Front End Control assembly J103 the test point voltages for the A13 RF
Front End assembly will not be correct.
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