HP 85047A contains HP 5086-7489 test port coupler which grossly fails simple directivity test (terminate with known-good APC-7 50 ohm load, and almost all source drive signal appears on the coupled port save for a notch/dip at mid-span.
As the history of the test set is not known, abuse is suspected.
Visual inspection inside the RF coupler subassembly shows no evidence of physical damage to any component or connection, nor absence of any component.
Question - is there any practical path to troubleshooting the coupler at the component level (with understanding that this would obviously negate any internal factory adjustments that might have been made at time of manufacture)?
Question - can the front APC connector assembly be removed from the coupler subassembly? If so, are there any torque limits I should be aware of (if there is a coaxial connection between the external APC connector and the coupler housing, I don't wish to damage that.)
Question - is the reference coupler (5086-7488) similar to the test port coupler (5086-7489) such that I could replace the coupler subassembly with a 5086-7488 (and ideally, transfer the external APC connector from the failed 5086-7489)?
Thanks very much for any advice!