A dynamic signal analyzer is an outstanding tool for characterizing and analyzing audio-frequency circuits. I was lucky enough to score a Hewlett Packard 35665A for a good price. It needed some love and attention to get it back in business, but I think we're there and it's been doing good work for me so far.
My first order of business was to get new feet. Apparently it's a thing that used HP gear almost always comes missing some or all of the feet. Luckily, the feet are mostly standard and are available on eBay from a number of sellers.
The other thing about used test gear in general is that it usually doesn't come with documentation. HP in particular has great documentation, but I didn't get any of it with my DSA. I've been working to catalog and accumlate all of the documentation for this beast. What I've got so far is listed farther down the page.
This instrument can save data and settings to an internal battery-backed memory. The battery was old but still working when I got it. The battery also keeps the real-time clock chip running. I was happy to find that the RTC seems to accept years after 2000, though I think maybe it doesn't automatically advance the year if it's out of a certain range? Anyway, the battery was pretty old so I replaced it with a new TL-5104 from DigiKey. The replacement was easy: totally drop-in, no modifications required.
If you've got the instrument open anyway, you might check in with GLK Instruments. They do an options upgrade for this instrument and have accessories and parts for other gear as well. They seem like nice folks to deal with.
Aside from the interal RAM disk, the 35665A can also save to 3½-inch floppy disks. I don't think you'll find these at your local office supply store anymore, but plenty of folks are selling them on eBay. Mine seems to work fine with both double-density (720kB) and high-density (the classic 1.44MB). Make sure to pick up some labels and felt-tip pens for the full retro experience.
Speaking of the retro experience, you can get a ThinkJet 2225A (the A is important; you want the HP-IB interface model) printer. This is the original thermal inkjet from HP. The story behind it is really interesting and is told in the May 1985 issue of the Hewlett Packard Journal. It seems like you can still get the cartridges new from Staples. I picked up a few new new-old-stock from eBay. They were still in good shape. They came sealed in metal tins! They include a little blotter that you replace along with the cartridge. The printer uses it to soak up ink used in cleaning the heads. The printer can feed single sheets or tractor-feed paper. Of course you'll want some tractor-feed for the full experience. You'll need an HP-IB cable too, one of the ones with black screws (the silver-screw ones have a different thread; I think they're less common). I haven't found a manual for this printer yet. If you know where I can get one, please let me know. I did find a Quick Reference that helped me out. The buttons on mine were worn off, so the little diagram and explanation of what they do was helpful. I've heard that some folks have trouble with the ribbon cable that connects to the cartridge. I guess the ink can leak down there and is corrosive enough to cause trouble even though the connectors are gold plated. Mine did have some dried-on ink that kept it from working right at first, but I was lucky enough to be able to clean it off with some 90% isopropanol and gentle scrubbing with a cotton swab.
Update: Stray Electron from the EEVblog forums dropped me a note to say that you're likely better off soaking the contacts in alcohol if they're gunked up rather than scrubbing. Apparently if the ink has had enough time to work on the plating, you can pop the contacts right off if you're not careful. He suggested that you may wish to store the ink cartridge contacts-up in an airtight container (a large pill bottle, for example) when not in use. He also mentioned that a potentially more reliable printer might be the HP 2671G thermal printer; some 2671's are text-only and they offered them with different interfaces, so make sure to get the graphics model with HP-IB interface.
If you're going to be saving a lot of files or titling prints, a keyboard is handy to have. Most any AT-style keyboard or PS/2-style keyboard with an adapter should work. I was able to get a new-old-stock HP (of course!) PS/2 keyboard from Amazon along with the necessary adapter. I did find one reduced-size AT keyboard that didn't work at all with the DSA. I'm not sure if it was a problem with the keyboard or if it was some weird compatibility issue.
I've been working on collecting all of the documentation for my Hewlett Packard 35665A dynamic signal analyzer. I've listed below all of the documents I know about along with a description. I've included the document itself as well, where I can. In some cases, I was able to find scans on the Internet. In other cases, I was able to get a physical copy of the document to scan it.
I hope you find this page helpful. If you have any questions or comments, please drop me a line. If this is the kind of thing you're into, you might enjoy our other work.Aaron D. Parks