I have a faulty S331D. It reports integrator failed at start and VNA integrator failed during self test. When measuring the return loss, I feel it works. You don't know where to look for the error.
Thank you
your unit has faulty RF section. most probably MMIC is cause of failure in such cases. is your unit a single port or two port version. I mean the two port unit comes with internal power meter option and has two N female test ports on the front panel