I have an 8563E that recently stopped detecting signals on certain frequencies.
I have discovered that the LO signal at the front panel LO SMA connector is absent (or weaker than I am able to detect with a 437B power meter) on those frequencies where the SA does not detect signals. On those frequencies where the SA is working properly, the LO signal strength is within specs with an output of 14.58-15.95 dBm.
The error messages that I see are generally YTO-related as well: 319, 334, 356.
I suspect that this dysfunction is a result of failure of the YTO, but I am not sure where to proceed from here. I have the Service Guide 08560-90149 and I have read it but I am still not sure of my next step.
The frequencies where things are properly working include:
The frequencies where there is no LO signal and the SA can detect no signals are:
I would appreciate any help from the group in guiding me on how to proceed from here.
Thanks in advance and best regards,