Al4 Vco Range Check With Oscilloscope - HP 8753E Service Manual

4. Check the counter reading at the frequencies indicated.
If the readings are within the limits specified, the probability is greater
q
than 90% that the fractional-N assemblies are functional. Either skip
ahead to the "A7 PuIse Generator Check" or perform the more conclusive
If the readings fail the specified limits, perform the "Al4 VCO Exercise".
q
1. Remove the W9 HI OUT cable (A14Jl to A7) from the A7 assembly and
connect it to an oscilloscope set for 50 ohm input impedance. Switch on the
analyzer.
Menus and Error Messages", for more information-on the F'RACN TUNE
mode.
3. Vary the fractional-N VCO frequency with the front panel knob and check
the signal with the oscilloscope. The waveform should resemble F'igure 7-17,
Figure 7-18, and F'igure 7-19.
If the fractional-N output signals are correct, continue source troubleshooting
by skipping ahead to "A7 Pulse Generator Check".
Source Troubleshooting 7-25
1