Service Guide 8-3
8719ET/20ET/22ET Receiver Troubleshooting
8719ES/20ES/22ES All Signal Paths Look Abnormal
RF Network Analyzers
All Signal Paths Look Abnormal
For the receiver to operate properly, the digital IF (A10) and 2nd converter assemblies
must receive signals from the reference assembly (A12). Those signals are the 2nd LO and
the 4 MHz signal.
2nd LO Check
To check the 2nd LO signal with the analog bus counter, press the following:
• If the counter reads 9.996 MHz, continue with “4 MHz Check.”
• If the counter does not read 9.996 MHz, perform the “Reference Assembly VCO Tune
Adjustment” on page 3-39.
— If the adjustment is successful and the problem is cured, for verification perform the
“Frequency Accuracy Performance Test” on page 2-34.
— If the adjustment is unsuccessful or the problem persists, replace the A12 assembly.
(A12 is indicated by red tabs.)
4 MHz Check
1. Switch off the analyzer.
2. Remove the Digital IF (A10) board (indicated by black tabs) and install it onto the
extender board (HP/Agilent part number 08753-60155, part of the 08722-60018 tool
kit).
3. Use an oscilloscope to observe the 4 MHz signal at A10P2 pin 6 which is labeled on the
extender board.
• If the 4 MHz sine wave signal is present at A10P2 pin 6, replace A10.
• If the 4 MHz sine wave signal is not present at A10P2 pin 6, check signal at A12P2
pin 36 by connecting a SMB(f) to SMB(f) cable and a SMB(m) barrel adaptor to
extend the “FN REF” cable front SMB connector. The “Ext Ref” cable (rear SMB
connector) does not have to be connected for this test. (A12 is indicated by red tabs.)
— If the 4 MHz signal is not present at A12P2 pin 36, replace A12.
— If the 4 MHz signal is present at A12 (but not A10), check the motherboard trace.
Preset
Preset
System
Meas
16 x1
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