Verifying The A12 Synthesizer Board; Troubleshooting Lo And Sampling Oscillator Unlock Conditions - Agilent Technologies PSA Series Service Manual

Troubleshooting the Synthesizer Section

Verifying the A12 Synthesizer Board

Verifying the A12 Synthesizer Board
Troubleshooting LO and
Sampling Oscillator Unlock Conditions:
Error messages
Sampling Oscillator Unlock, Failure acquiring SO frequency
lock
This message appears when the 600 MHz signal to the A12A2 is not
present. Check the MMCX cable connections on A12W2 between the
A12A2 and A12A1 boards.
1St LO unlock, failure acquiring FracN frequency lock
This message will also appear when the 1st LO is unlocked for many
reasons. It will often appear whenever the sampling oscillator unlock
message is displayed.
Perform the Auto Align All routine before beginning troubleshooting.
NOTE
The LO power is adjusted during this internal alignment process.
Input signal check
Measure the sampler output from the A21 LO distribution amplifier.
Since removing the LO signal will cause a 1st LO unlock and an
unstable measurement, you must inject a signal into the LO amplifier
and measure the signal at the sampler output port.
Please use care when moving the semi rigid cables since they can crack
NOTE
or break, especially at the connector solder joints. The almost invisible
cracks can cause residual responses to appear.
Power down the PSA.
Disconnect W35, the semi-rigid cable from the LO IN port of the
A21 LO distribution amplifier.
Connect a cable with SMA connectors to a source capable of 4 GHZ and
+10 dBm output power. Measure the power level at the end of the cable
with a power meter to assure the proper level.
Disconnect the power sensor, and connect the cable to the LO IN port of
A21.
Disconnect the semi-rigid Sampler In cable W24 from J1 of the A12
synthesizer. Connect a spectrum analyzer to the end of this cable.
114 Chapter 5