OK, Finally got the time to play with this, here are few notes that may help others. I ordered an incomplete 8665B and got most of the things sorted.
I also have a 8665A coming over at some point.
And a few more
A few of the errors I had:
+1078311 COAX DSC
-10124 311 HF DRV J6
-31302311 MOD DIST NSM OSC - J2
+4101311 MOD DIST NSM OSC
-31467311 MW ASSY / GAAS dividers U17 J4
Replaces and tested all the coaxes from COAX DSC and Reference board solved a lot of troubles, the previous guy was not gentle with it.
Then took the U17 took it out of the socket cleaned it with ISO alcohol and reseated it, warmed up the pins and voila another error gone
HF driver gave me a headache, the trim pot was on the max and could not reach it's voltage, so that needed to be addressed, tested with another board and it worked.
Repeat the CAL every time and ...
Still have:
+5030311 REF OSC / STD 1nn / FAST 2nn /
3nn
+6031311 ATTN or 2GHz ATTN, in our case Attenuators
This unit had the option 001 and I only have a STD oscilator, the ROM seems to expect it, hoping that I will get one with the one I ordered. I don't (yet) know how to tell it I only have a normal oscilator, I did notice the above normal output at +15dBm, tempted to add an attenuator in the middle. I do have the same error if I put my 10MHz source and it works as intented switching between internal and external ref.
I had another issue with the attenuators, I had the bad U32 in the I/O board that rom keeps the attenuator cal, so it's important to secure that ROM with new attenuator module. I may have to find a way to calibrate these little buggers later. But I may also find the original ROM too... I'll read it and hexdump it and see if I can make sense of it.
My recommendations: Start with the section 2d and 3-1 of the Assembly level repair and go from there, take your time and get the things sorted, mark all SMB coaxes if they are not anymore. Test coaxes one at the time rinse and repeat.