Service Guide 7-23
8719ET/20ET/22ET Source Troubleshooting
8719ES/20ES/22ES Band-Related Problems
RF Network Analyzers
• If greater than −5 dBm for DAC numbers from 50 MHz (DAC # ≅3650) to about
1.1 GHz (DAC # ≅4095), troubleshoot the cabling and components from A5J3 (A25J3
for 8722ET/ES) to the R sampler assembly A64J2 (refer to the overall block diagram
at the end of Chapter 4 ).
• If less than −5 dBm at A5J3 (A25J3 for Agilent 8722ET/ES), the problem is in the
A53 mixer/amp, A57 fixed oscillator, A5 (source switch), or A6 (source switch) or A25
on 8722ET/ES models.
3. Measure power at the A53 end of cable (W6).
• If power is greater than +8 dBm, A6 (source switch) and A55 (low band YIG) are
good.
• If power is less than +8 dBm, continue with step 4.
4. Measure power at the A6 end of cable (W7).
• If power is greater than +8.5 dBm, A6 (source switch) is good. Replace A55 (YIG).
5. Measure power on the A5 (source switch) end of (W42).
• If the power is greater than −5 dBm, replace A5 (source switch).
• If the power is less than −5 dBm, the problem is the A53 mixer amp or the A57 fixed
oscillator. Replace the A53 first and if the problem persists, replace the A57.
Mid Band Problems: (8722ET/ES Only)
1. Press the following:
(SRC tune in the mid band is capable of tuning the instrument from about 2.4 to
5 GHz). Loss of lock in mid band only may likely be due to a bad cable or connection.
2. The following components may be at fault. Refer to the overall block diagram at the end
of Chapter 4 for information.
3. Since the analyzer phase locked in lowband, all of the phase lock circuitry is working.
Look for low power as a cause of phase lock errors.
4. Check power at A25J3.
• If the power at A25J3 is less than −1 dBm, check the insertion loss of A5 (source
switch), A6 (source switch), A25 and the associated cables.
• If the power at A5J3 is greater than −1 dBm, the problem is probably above 5 GHz.
Proceed with the next steps.
A5 (source switch) A6 (source switch) A58 M/A/D/S A55 YIG 1 A25 (switch)
System
4000 x1
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