I am working through the repairs of my MS2651B spectrum analyzer, I have now got the display working 100% and fitted a new front end mixer which now displays signals on the screen but I am showing several fails during self calibration. In log mode (default) the signal line is sat at just under the top line of the screen which indicates a failed level test. In linear mode (not ideal) the noise floor drops to near the bottom of the screen and signals are displayed correctly and the analyzer is usable.
One of the many self cal fails is the 10db IF amp and many of the other fails follow on from the IF stage so my best guess is that the IF amp is affecting the expected levels further down the chain including the LOG detector. My problem is that many of the components seem to be marked with in house codes and many hours of searching have not turned up any usable part numbers. From what I can work out from the component layouts and matching it to the block diagram, the suspect component is marked as RF62, but I just cannot identify what the actual part number is. I have included a few pictures of the board to try and help with the identification.
Any help or suggestions greatly appreciated.. Karl