I've repaired two of these, a standard one and the rack mount version, both have the original leads which are in the same condition as yours, I may have to replace them with modern stuff if they get worse. NOS leads do appear from time to time, but are expensive & get snapped up quickly, also no guarantee they won't also have gone hard with age.
Yeah, I wouldn't use NOS to replace these anyway, they're just as old. That would be like buying NOS vintage electrolytic caps.
But I'd love to get my hands on an original probe!
I've been toying with the idea of replacing the leads with BNC connectors - coax for the DC and COM leads, and twinax for MA/OHMS (triax is just too expensive). I'd just have to drill out the chassis holes a smidge, and I think there's room to fit all three without interference.
Despite being on different continents for 40 to 50 years, both had the same 1500uF low voltage electrolytic cap fail open circuit, all the others tested fine & remained. The Sprague bumble bee caps had slight leakage and were all replaced.
One had contact problems with the chopper lamps and the other a tube had failed with grid leakage.
After poking around some more, I think my plan is to replace the 1500uF/10V can and leave the rest of the electrolytics unless they actually show that they're failing. The little 50uF/6V ones at C107/C110 look to be a pain in the butt to get to, the 50uF/25V meter stabilizer (what the hell does "semi-polarized" mean, BTW??) is in an awkward spot, and getting at the terminals of the double 20uF/450V can looks to require fairly major disassembly. I mean, come on, HP, why didn't you anticipate someone needing to service these things 53 years later?
Since mine is a pretty late model, the paper Sprague caps are the later style (labeled with words, not color bands). I'll test them of course, but they seem to be working fine for now. Or maybe not; I've got .47uF on hand, so I guess there's no reason not to replace them anyway. I was surprised to see orange drops on the modulator board - I'm pretty sure this is the earliest piece of equipment I've seen with those. They appear to be factory (uh, HP, not you - just noticed your username
), because the solder joints are clean and identical to all the others.
I don't know what the switch wafers are made from in the later one you have, but the service notes warn that certain plastic types will be damaged by switch cleaner. In at least one of mine they are cracked, maybe a previous owner didn't know about this.
I'm staying far, far away from that switch. It's a different color in mine, but the Army manual that covers my version has the same dire warning. In fact, I cleaned the contacts on the chopper bulbs by spraying the pins, working the bulb in the socket, then repeating, just to avoid any drips.
The service notes are on the hparchive site; http://hparchive.com/hp_equipment
Thanks, I appreciate that!