152 Keysight N9038A MXE Service Guide
Input Selection & Level Control
Input Selection & Level Control Section Troubleshooting
Verifying Input Selection LED Control
1. Remove the instrument dress cover (MP24) and top brace (MP10). Refer to
Chapter 18, “Assembly Replacement Procedures.” for instructions on
removing these covers.
2. Remove the hardware that attaches the front frame assembly to the
chassis and slide it away from the rest of the instrument, but do not
disconnect W8 which connects it to the A8 Motherboard assembly. Refer
to Chapter 18, “Assembly Replacement Procedures.” for instructions on
removing the front frame assembly.
3. Referring to Figure 4-16, disconnect W6 from the A23 Limiter assembly
LED Drive Output (P2).
4. Turn the instrument on and allow it to complete its boot up process,
ignoring any error messages.
5. Tune the instrument to a frequency of 10 MHz with a span of 0 Hz by
pressing FREQ, 100 MHz, and SPAN, Zero Span.
6. Switch the instrument to the primary RF Input by pressing Input / Output,
RF Input, RF Input Port, RF Input.
7. Referring to Figure 4-18, verify that the DC voltage levels on the 4 pins of
the A23 Limiter assembly front panel LED Drive Output (P2) are as outlined
in Table 4-3 when the RF Input Port is RF Input.
If the voltage levels are incorrect verify that the A23 Limiter control
voltages coming from the A21 RF Preselector Input assembly are correct
before replacing the A23 Limiter assembly. This can be verified in the A21
RF Input Assembly section of this chapter.
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