Thanks for all the super helpful responses. I now have a frame coming (thanks again Kurt)! While I have been waiting on pieces needed to reconstruct the RF section, I have been working with the IF section and I have it working pretty well and managed to get all the options enabled (except AY5 - see below). Here are a few things I learned that might help others:
1) The HP 89441A IF section is the same as the 89410A. If you enter service mode (the password is 1125) you can change which one it identifies as.
2) As far as I can tell, all of the options in the 89410A / 89441A IF section are software options except for UFG (4-MB Extended RAM and Additional I/O), AY5 (Precision Frequency Reference), AY9 (Extended Time Capture), and AY7 (second input channel).
3) There is a really nice "hack" to enable all the software options. Just Google for it.
4) You can convert the UFG options (4-MB RAM) to the UTH option (20-MB RAM) by adding a single 16MB RAM. Order Micron MT8D432M-6X from eBay etc. This is a really nice addition that costs about $10 to do so well worth it. You don't even need to change any of the software options - as long as you have UFG installed adding the additional SIMM will automatically cause UTH to show up as installed when the system is powered on.
5) If you have an 89441A system, you won't have option AY5 in the IF section, but that is OK - it is usually just installed in the RF section unless you have option AY4 which deletes the precision reference from the RF section.
6) There is a firmware update available from Keysight that, once installed, allows software options B7A, B73, B79, and 080 to be enabled (you still need to do the options hack to actually turn them on). However, these are all for testing obsolete cell phone standards, so I am not sure how much use this actually is... Get it here:
7) There is a piece of polyurethane foam between the main chassis and display section of the 89410A / 89441A. If you are servicing the unit anyway, I recommend removing this foam and cleaning up the residue as it turns to sticky conductive, corrosive tar. The foam isn't really needed for anything so the safest thing to do is just remove it. Lots of acetone will be needed to clean up the mess!
OK, with that contribution, I have another ask for the group. I am apparently missing the little metal clips that attach the front frames of the RF and IF sections together. The locking feet that attach the rear frames together came with the unit (and I have managed to use HeliCoils to repair the torn-out holes in the IF section frame where they mount), but the clips for the front were not included for some reason. The photo below shows the parts I am looking for. It looks like I need 4x of them along with the 8x metric screws needed to mount them. These same clips seem to have been used on the 8566 / 8568 spectrum analyzers and also appear to have been included in the locking feet kit (5062-3999) but I haven't managed to find an HP part number for the clips themselves.
The last piece I am looking for, and this is purely cosmetic, so I guess it isn't the most important, is the plastic trim for the top. I would be looking for the grey (not the older olive) color one. This was used on a lot of gear, but they are commonly missing too. I figure it is worth a try...
Thanks again all for the help.
-Matthew D'Asaro
medasaro
Tom Phillips