I have a 8920A that had SA readings that were approximately 13db low and failed RF Diag tests for SA vertical sensitivity (low) and all three receiver down converter tests (low).
I followed Rick's advice and replaced U4 on the receiver board. I used a MAR-7SM+ as a substitute for the original MSA-0786, thanks to Alessio, which measured 2.2V IN and 4.2V OUT. Result?.....no more failures and the SA is reading input signals correctly!!
Note: the new new part measures 2.7V IN an 4.1V OUT.
Thanks guys,
Greg
WB9TRO?
