All Signal Paths Look Abnormal; 2Nd Lo Check; Mhz Check - Agilent Technologies 8719ET Service Manual

8719ET/20ET/22ET
8719ES/20ES/22ES
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:
PRESET: FACTORY
Preset
SERVICE MENU
System
ANALOG IN Aux Input
Meas
• If the counter reads 9.996 MHz, continue with
• If the counter does not read 9.996 MHz, perform the
Adjustment" on page
— If the adjustment is successful and the problem is cured, for verification perform the
"Frequency Accuracy Performance Test" on page
— 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.
Service Guide
Preset
ANALOG BUS ON
COUNTER: ANALOG BUS
3-39.
All Signal Paths Look Abnormal
16 x1
"4 MHz Check."
"Reference Assembly VCO Tune
2-34.
Receiver Troubleshooting
8- 3