Electro Fan asked my opinion about my 7904 mainframe vs 2465B (back in Oct, sorry). Here's my lament.
In an ideal world, the 7904 plus a bunch of plugins is simply an unbeatable setup. It is very good at a lot of things, and can do just about everything. I had slow and stable time bases, I had fast and cranky ones, I had HV amps, current amps, a super sensitive diff amp, a sampling head (never got it working), a pretty good curve tracer, and I could have had a spectrum analyzer if I found one whose price matched its limited capability. The front panel is well laid out, feels great, and is super easy once you get the hang of it. It's worth dimming the lights in the lab just to see the backlit switches in their full glory. Stunning.
So why did I get rid of it and get a boring old 2465 instead? Quick answer: lack of space and time.
First space: this thing is huge and puts out a ton of heat. Don't stack anything on it, and get long probes and clip them so they don't drag your project off the bench. I put my mainframe on a scopemobile which doubled my bench space but really cut into floor space. Now try to find room for 16+ plugins that just don't stack very well thanks to their springy ESD fingers. (Why so many plugins? Because you need certain combos to get good readings. You don't want to feed the 7CT1N with a fiddly fast amp, no point to the 7B10 if you only have 7A18s, etc. You'll get a feel for which ones work well together, but first you need to obtain them...)
And time: at least 20% of my plugins tended to be in the repair pile. These things are old and oxidized, full of tants, and a lot of signals route through the front panel (no digital encoders here). Buy contact cleaner. A LOT of contact cleaner. Pray that all the plastic shafts and electromechanicals don't crack because they're impossible to source (maybe 3D printing can help). Don't touch the trimpots because they can be hell to stabilize. Need to probe a plugin while it's powered? Guess what? That takes another plugin! Google "plugin extender", lot of options but all of them are a PITA and you end up debugging the extender as much as you do the plugin. Fast plugins break a lot more often than the slow ones, and they're MUCH harder to fix. And I think I remember needing to be careful of semi-high voltages running bare-leaded next to signals, easy to fry.
Back in the late 90s, when I started my 7000 series habit, I would clean up at surplus sales. You could get a set of 7A18s and 7B53s for $40 total because these shops were sick of them collecting dust. I found a 7A11 for $30 because the seller didn't realize it was any different (it quit working a year later). I bid on a lot of 5 plugins and found one of them was a working 7CT1N, which alone was worth 3X what I paid. Easy to get hooked. By 2008, though, it was mostly dried up. Heck, the whole surplus test equipment market seems to have disappeared from the Bay Area, and the 7000 series equipment I see at the De Anza flea market is stupid expensive or broken.
An all-in-one seems great, doesn't it? Not really... Any time I wanted to use the curve tracer, I had to slide all the current plugins out, slide the 7CT1N in, plus the plugins it needs, reseat a few times until the traces were stable, use it, and restore everything when done. It's a lot more effort than just pulling a curve tracer off the shelf, and can be infuriating if you have to take apart a working probe setup.
One day I realized I was spending almost many hours keeping my equipment happy (repair, procurement, inventory management) as I was keeping my designs happy. So, in a fit of despair, I sold the entire package for an absurdly small amount. I couldn't bear it.
So far the 2465B is treating me well. It doesn't respond instantly the way the 7904 did, and it isn't anywhere near as flexible, but I haven't had to debug it even once (yet). I love that.
So, if you have tons of time and tons of space, and if enjoy figuring out if noise is in the signal or just in the scope, and reseating plugins, and if you always want to be on the lookout for more plugins, and you enjoy coming up with clever fixes, I heartily recommend the 7904. It's simply beautiful. I miss mine dearly.
But I'd never buy another one...