5-14 Service Guide
Power Supply Troubleshooting 8719ET/20ET/22ET
If the Green LEDs of the Post Regulator (A8) Are Not All ON 8719ES/20ES/22ES
RF Network Analyzers
Remove the Assemblies
1. Switch off the analyzer.
2. Install A8. Remove the jumper from A8TP2 (AGND) to chassis ground.
3. Remove or disconnect all the assemblies listed below (see Figure 5-5 on page 5-9).
Always switch off the analyzer before removing or disconnecting an assembly.
Digital IF (A10)
Phase lock (A11)
Reference (A12)
Fractional-N analog (A13)
Fractional-N digital (A14)
GSP Interface (A22) (disconnect A17W2)
4. Switch on the analyzer and observe the green LEDs on A8.
• If any of the green LEDs are off or flashing, it is not likely that any of the assemblies
listed above are causing the problem. Go to “Briefly Disable the Shutdown Circuitry”
on page 5-15.
• If all green LEDs are now on, one or more of the above assemblies may be faulty.
Continue with the next step.
5. Switch off the analyzer.
6. Reconnect cable A17W2.
7. Switch on the analyzer and observe the LEDs.
• If the LEDs are off or blinking, replace the A19 GSP assembly.
• If the LEDs are still on, continue with the next step.
8. Switch off the analyzer.
9. Reinstall each assembly one at a time. Switch on the analyzer after each assembly is
installed. The assembly that causes the green LEDs to go off or flash could be faulty.
NOTE It is possible, however, that this condition is caused by the A8 post regulator
not supplying enough current. To check this, reinstall the assemblies in a
different order to change the loading. If the same assembly appears to be
faulty, replace that assembly. If a different assembly appears faulty, A8 is
most likely faulty (unless both of the other assemblies are faulty).
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