7-16 Service Guide
Source Troubleshooting 8719ET/20ET/22ET
Broadband Phase Lock Problems 8719ES/20ES/22ES
RF Network Analyzers
Check the VCO (A14) Range with Oscilloscope
1. Connect an oscilloscope to A14TP1 (labeled VCO/2, yellow tabs- rear multi pin
connector).
2. Press the following:
3. Vary the fractional-N VCO frequency with the front panel knob.
4. If the waveforms do not resemble Figure 7-3 at the frequencies indicated, replace A14.
(The amplitude of the waveforms will vary from 3V to 10V p-p.)
Figure 7-3 VCO/2 Waveforms at A14TP1
Substituting Tuning Voltages to Check the VCO
The tuning voltage range of the VCO is approximately +1 to +14 volts. This procedure
substitutes power supplies for the normal voltages from A13 to check the frequency range
of the A14 VCO.
1. Turn off the analyzer.
2. Remove the A13 assembly (orange tabs).
3. Put the A14 assembly on an extender board. It is not necessary to connect the cables
while the A14 is on the extender board.
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