OK, this thread is a tale of 2 HP 8656B generators. I actually came by them 'by accident' as the the first one was bundled in with a power supply that I wanted. It was non working but complete - for the sake of clarity I shall call this #1. A quick inspection revealed a 'popped' inlet filter and the typical RIFA stank. The inlet filters are still available (at a rather salty price), so one new Schaffner FN370-2-22 and the instrument was up and running - or so I thought... Looking at a few random frequencies on a spectrum analyzer showed that the level was down a few dB, but other than that basically following the attenuator settings, and the frequency was pretty close. The fact that my work has a fairly new Siglent SA for EMC pre-testing was turning out to be pretty handy.
Anyway, I happened to send some pics of the working generator back to the guy I bought it off, and he came back to say that he was moving office, and had an incomplete 8656B spares unit, which I could have (as I recall) for the equivalent of about USD30. Sounded good to me so I ended up with another, somewhat more sorry looking patient, unit #2. This one was missing the power transformer, and once again, the inlet filter had vomited its insides.
Some time later, in the course of another thread here on EEVBlog,
https://www.eevblog.com/forum/testgear/fool-for-the-8656a-sig-gen/, user Brumby mentioned that he was breaking a 'B for spares. Hmmm, should I do the same to my 'spares' 'B, or fix it up? Well, TEA is a harsh mistress, so fix it up was the way to go. Do I need 2 RF sig gens? No... I didn't even need the first one at the time, although now I'm starting to get into this 'RF stuff'.
First job was to check on the state of #2 - easy to do as I just swapped over the rear panel from #1, which contains the transformer and inlet filter. Sure enough, #2 powered up and levels and frequencies were ok. Well, other than being 6dB down below 100MHz, and 2dB down on the rest of the range. The latter could be put down to measurement set up (i.e. cables or whatever).
So to conclude, at this point I had 2 (hopefully) mostly functional HP 8656B signal generators, but only 1 working power supply between them.
Edit: Just for fun, added a pic of unit #2 at 990MHz as measured by an older relative (reading on the HP 5245L is .95GHz on the dial + 40000.019KHz on the display)