Yesterday, I had a pleasant visit by DC1MC who schlepped his Anritsu Signal Generator to my workbench for a TEA repair day.
Set up some instruments to diagnose that beast, first issue found was too low a signal output level below 40MHz.
After some debugging, the culprit was found and removed from the board:
It's a balanced diode ring mixer that lost most of its output. By some lucky coincidency, I had a spare Mini-Circuits mixer around, not an exactly fit for the PCB layout, but does the job well.
Second, the sig gen had random output levels over all frequencies when switching the mechanical attenuator. Same problem as this one:
http://wunderkis.de/mg3633a/repair1.html So quite an easy fix, but somehow labour intensive.
Third issue, after some digging looked quite similar to this fault:
http://wunderkis.de/mg3633a/repair2.html Indeed, it's been the very same capacitor that had to be replaced.
So finally, everything put together and assembled, it's a happy signal generator again: