One of my hobbies is audio/stereo. I often need to know the condition of diamond stylus' that I pick up used or to gauge wear as new ones are in service. While there are some specific microscope kits that have been made to do this, they're all quite expensive and rare. Being retired, I can't justify the expense for such a specific use thing.
Was walking through the local thrift store a few months ago and one of the things on the shelf was a Tasco microscope. One of the older "kids exploration" microscope kits. ”Model no. 952”. Still in its original wooden case with slides and the paraphernalia needed to make more. Was only 15 bucks so I grabbed it. I figured if nothing else, it would be an inexpensive exploration of using a microscope to try and get an idea of stylus wear.
Japanese manufactured, so I'm guessing somewhere around 1960's/1970's vintage (edit: found a sales catalog from 1968 with this microscope kit in it and a couple ebay ads with 1970 and 1971 dates on the included paperwork).
Seems to bear more than a passing resemblance to a Kyowa brand microscope. Kyowa built and rebranded for other brands, and Tasco was one of them. There's also some anecdotal evidence that the optics were made by Nikon for Kyowa, but only anecdotal, so take that for what it's worth. (Edit: turns out it's made by Carton optics in Japan)
This would have been considered an inexpensive "child's microscope" back when it was made, but it's heads and shoulders above what you get in a child's microscope now. This is all aluminum, brass or glass. No plastic anywhere (well, the light/mirror case is plastic). Today's ones really are cheap toys compared to this and I wouldn't even try using one of the modern ones for this purpose.
Once I got around to checking out, it was obviously old, forgotten a long time ago and neglected. Everything was stiff or just plain ol' locked up. The fine adjust, well.....didn't. Optics were all pretty dirty and greased up.
So I started pulling it apart. Yep, anything that was once grease was now glue. It was all so bad, I had to resort to an overnight soak in varsol to get the bits clean. IPA wouldn't even touch it. In the process, I discovered why the fine adjust wasn't working:
That's part of the fine adjust mechanism. Made of zinc (or zamak) and zinc pest had gotten to it. the only part not made of aluminum or brass. It started crumbing in my hands as I was removing it. It was also probably broken off when someone tried to move it with the grease that had turned into a sticky, thick glue.
That broken piece is where a ball bearing rides on a cone for the fine adjust. You can see by the walls it's pretty thin and weak to start with. They even made it weaker by punching that hole straight through it to locate the ball when all they needed was a dimple. Oh well, cheaper to manufacture that way I guess. Not surprising considering this was never a "serious" microscope. A heavy spring pushes down on the top square boss to load the ball bearing against the adjusting cone and even that was starting to crumble from zinc pest.
So I had to do something before it all completely crumbled to dust (and I would no longer even have it for a template) or just give up on the fine adjust features altogether. Luckily, I have a vertical mill in my garage, so a couple hours later:
Better than new. I added a little extra where I could around the ball bearing block to give it a little more strength nd left extra thickness where ever I could. Made from a left over scrap of 6061 billet aluminum, even the material itself is stronger than the zinc (or zamak) casting. More than enough for the intended use and will now live as long as the rest of the scope does.
The optics just needed a disassembly and cleaning. The grease (after a thorough cleaning) just needed new grease.
It all moves smoothly and easily now, just as it should.
A little scrap wood, some led lamps from amazon, and a wrap of scotch tape to temporarily make a crude xy adjustment/holder:
Not too shabby. A look at a messed up stylus from an AT132EP, nude mounted diamond:
The last pic the optics were a little smudged up from my greasy fingers after greasing all the mechanisms. I obviously touched something inadvertently. Optics obviously need a re-cleaning.It also shows the light reflecting off the wear facets, which is what you usually want to see in order to gauge stylus wear.
Still playing around with lighting, but pretty good for a cheap little microscope. Works good enough for a quick inspection as to condition.
Those are all right around 200-240x mag, which is right around where you need to be for stylus wear assessments.
The really nice thing about it is the optical tube moves up and down (not the table) for focusing. That means it has more travel (than the moving table) and I can get any stylus/cart standing straight up under it without any clearance issues and still have lots of "focusability'. Great for that "front on" view for assessing azimuth wear, as you can see on the AT132EP tip above.
It had an azimuth issue, done by a PO at some point. Kind of weird that a T4P cart (P-mount) would have an azimuth issue, as that was one of the issues the P-mounts were supposed to eliminate. But there's no denying the wear evident in the pictures....I guess the saying "as soon as you make something foolproof, they invent a better fool" might apply to this old cart.
Still needs more work, but under 50 bucks into it and it's at least usable. That's a success in my books!
