Test Equipment Anonymous

All y'alls may know by now that I recently scored one-a-deez on my latest outing to our local Vintage Radio Museum.



It lights up and digits move, but there's a problem with one of the buttons that randomly sticks on, which makes none of the other buttons work. If you thump the panel it pops loose and the other buttons work for a few seconds until it sticks up again. I've disassembled it from the Star Trek shuttlecraft shell to try and figure that out, but this afternoon I was painting something else, so I decided to do the shell at the same time. This shell is a truly nauseating shade of brown in real life; these photos simply don't do it justice. You'd swear it had 20 years of nicotine all over it.



First, the rivets holding the handle need to come off; these escutcheon-stickers are the first step. I tried a little heat on one of the less conspicuous ones on the bottom shell, but it did nothing for the adhesive and deformed the sticker. The rest I am removing with a putty knife at room temperature. To get the putty knife started, I gently lift the edge of the sticker with a thin paring knife...



...and then it's just a matter of working slowly and carefully across the surface. I changed to a clean putty knife with a blunt edge; this keeps the putty knife from gouging bits of plastic out of the plastic underneath. These will make the sticker all lumpy when you reapply it.



Now that all the stickers are off, I can move on to drilling out the rivets in the handle...



The trick with drilling out rivets in plastic is to use high speed and light pressure; this keeps the drill from gouging into the rivet and just making it turn. Just dab the drill gently at the surface of the rivet for a second or two at a time and lift it away to keep friction from getting it hot and melting the plastic.



Once you get down to the washer, a Philips or Pozidriv screwdriver in the center of the rivet is all you need; a whack on the butt of the screwdriver with the heel of your hand will pop it through. After that, the usual washdown with clean towels and Windex followed by washing everything with a fresh towel wet with IPA and it's ready for paint.



... and now it's sitting outside, baking in the sun.

mnem

WTF? Black? Navy Blue?

Huh?

Can't do it black. I mean med already claimed Bluke

A reasonable haul, with the Fluke the pick of the catch.

I've got a Micronta FET multimeter like that which came from a swapmeet for £5, because I hadn't bought anything else. There was the consolation that it had good batteries (the 9V battery would cost at least £1) and it came in its original box. It looks like it has had hardly any use. No leads, but I cut the shields off a spare pair and they fit. I found the schematic and tweaked it to read accurately against the Brymen. I don't use it much.

bd139 wrote: ↑Wed Jun 19, 2024 8:10 amCan't do it black. I mean med already claimed Bluke

I painted it blacker than your soul!!!

I had another project I was working on that was getting satin black paint, so it got that too. The paint I used was Krylon Plastic formula; it's supposed to be used without primer for best adhesion, but I'm not 100% happy with the results; the other part (above) came out with a nice even satin finish, and you can even still see the LASER-etched Sabrent logo if the light hits it just right.

The shell on this 8860A just beat me up: First with random fisheyes in the first dusting coats, even though I wiped the entire thing down with IPA twice before I started; then after it filled out and looked good in final coats, it dried with very varied gloss level on the sides, splotchy even.

mnem
pretty sure I won't GAF once it's in the stack and has a little dust on it, tho...

Okaaay... now the paint has cured overnight, I can start reassembly. A little trial & error and these appeared to be a perfect fit; nice that I had some in SS.




Due to small clearance between the shell and the metal chassis inside, the rivets have to come through from the inside. Fitting these rivets required omitting 2 of the original washers; I'm using just one under the swage end of the rivet. To ensure good bite, I'm pressing down on the washer while pushing up with the riveter/squeezing the grips. It's a fiddly bit and easy to lose coordination, but I managed without wasting a single rivet.




Once the handle assembly is riveted back on, time to get the nameplate-stickers ready. I stick them to a ziplock baggie to protect the adhesive while I scrub them with IPA.




After that, I apply a little heat (big paint stripper gun on low) to reactivate the adhesive. Identify and locate exact position of each sticker such that the patterns of ripped off adhesive match and the sticker goes back oriented exactly where it was originally; this keeps it from being all lumpy.




Here's the finished inside showing the rivets all nice & flush...




... and the top with nameplates reinstalled.




Next installment, I'll tackle this.

mnem
*tinker-tinker-tinker...putter-putter-putter...

This one actually made me step back and sleep on it; my original thought was to somehow try and hack a thin tactile switch in there, as I'd just done similar mod for the power button on some keyboards I fixed for wifey's music class. That would require that I cut the trace to the switch, or separate the layers and try to slip something in there to insulate the collapsed contacts.

Hmmmm... separate the layers...




After sleeping on it, I realized that hacking a tactile switch in there was likely to require soldering at that pin header; this risked melting a crimped connection. I decided to first try a bit of a ghetto-fab, last-ditch hail Mary attempt before resorting to hacking up the membrane keypad.

I carefully separated the layers of the membrane with a paring knife, then slid the round end of a Dremel bit inside such that it puckered the membrane in the correct direction. After that, a really quick blast of superheated (420°C) air from my rework station right at the pucker made it bubble out again.

Repeated testing indicated it did not want to collapse again, so I resealed the membrane and reinstalled it all. Testing with the panel just plugged in revealed that the short was gone, and all buttons now worked normally. The [OFFSET] button didn't have quite the same pop as the other keys, but honestly it will probably outlive me, given how often I'm likely to use that function.




Now that I'm satisfied it is mostly fixed, time to take a quick tour of the insides so all y'alls can have your fix of TE pr0n...




...and that brings us to these little switches. Those of you who own one of these might have noticed that it was only displaying 3 digits; that's not a fault, it's S1 above. In this position, it enables 3-digit fast-sampling mode.



Here's what was hiding under that pretty aluminum plate; all the [INPUT] section. When I took the panel off to work on it, there was nothing connected to the input jacks. That, and the fact the shell only had two screws in it, suggests to me it was either robbed for parts to fix another 8860A, or someone took it apart, figured out what was wrong with the keypad, and back-burnered it until it wound up a donation.

Everything inside this unit was so very clean; I just dusted it out with a balloon pump. I did not touch anything in here without gloves on or using freshly-cleaned hemostats.

Yeah, yeah, I know... I'll worry aboot that after I get a little testing done.

Careful inspection with a flashlight did not reveal any evidence of tant-juice on any of the boards, so I'm going to just move forward with the pr0n for now.




Here's the lovely linear PSU section, showing power and AC voltage-selection switches. That BNC in the lower right is the remote trigger input.




Here's the guts top-down; lighting makes different items more visible so I just put up both pics.




This view shows off the Option 5 HP-IB quite nicely; you can see the IDC ribbon cable snaking around the XFMR from the HP-IB port on the back and its interface card plugged into the mainboard. Remember modular design...? Yeah, yeah, yeah... I'm fucking old.


Allrighty, that's it for nekkid 8860A pics; next post will be testing and glam shots.

mnem

So here's our first peek of it all back together; I think I had to pop the cover off again real quick to change that S1 inside after this shot. Still... pretty effing sweet.




And here's the back; no rear inputs, but it does have the HP-IB and that plastic cover that always gets smashed is intact. I should probably print some covers for those ports...




Initial testing with my bench power supply and AC line voltage gave valid "sanity check" results, so I dug out my sad little collection of voltage and resistance references. DCV checked similarly close as this at 2.5V, 5V and 7.5V settings.




This standard is configured as 29 x 5K315 0.1% resistors (154K135 nominal) in series... I'm gonna call that a




Here it is measuring the 200R from that set of .01% resistors we all got in on while I was up in the GWN. All of them test similarly close. I might putter around with one one of my arbs on a transformer to do some side x side validation against my 3478A on ACV ranges; but at this point, I'm confident enuf in it to start looking for a spot on the shelf to put it... at least until I'm ready to order replacements for all those beady little bastard tants.




And finishing up, I pulled out the old Canon G10 for a quick family portrait. There's that yellow & black @bd139 was craving...

mnem

Zenith wrote: ↑Wed Jun 19, 2024 10:20 am A reasonable haul, with the Fluke the pick of the catch.

I've got a Micronta FET multimeter like that which came from a swapmeet for £5, because I hadn't bought anything else. There was the consolation that it had good batteries (the 9V battery would cost at least £1) and it came in its original box. It looks like it has had hardly any use. No leads, but I cut the shields off a spare pair and they fit. I found the schematic and tweaked it to read accurately against the Brymen. I don't use it much.

Ehhh, some would argue the 85A in "it has words on the screen" condition was the pick of that litter, especially for 50 bucks.

I've had one of those Micronta Dual-FET meters in my stable for ~4 decades... they are a null-measurement meter, so as close to a VTVM as you're gonna get in solid-state, plus battery-op makes them very convenient. I don't use mine that much either, but when I want it, I'm glad I have one.

I actually went to the swap meet looking for a parts unit for my current one, which has a suspect shunt in the mA section. This one is so much better condition overall, and it looks like it maybe has just a bad 9V pigtail.

I actually need to print up a AA->D-cell adapter so I can triage it...

mnem