Here’s another great video teardown from TheSignalPath:
In this episode Shahriar repairs an Anritsu 37347A 20GHz Two-Port Network Analyzer. The unit does not boot up and as a result its internal state is unknown. The boot fault is traced to a bad RTC module which has a built-in integrated battery. A replacement unit is located which allows the unit to fully boot.
The instrument initially displays an unlock condition on the internal PLL. This problem is resolved by loading the PLL calibration files from the HDD. The complete block diagram of the unit is examined in detail and an unusual PLL intermittent locking problems is demonstrated. Various measurements on several of the internal PLLs confirm their functionality. As a final experiments, the instrument is calibrated and the S-parameters of a tune-able band-pass filter is measured.
More details at The Signal Path homepage.