Tektronix’s Ceramic CRT Production And The Building 13 Catacombs

As a manufacturer of test equipment and more, Tektronix has long had a need for custom form factors with its CRT displays. They initially went with fully glass CRTs as this was what the booming television industry was also using, but as demand for the glass component of CRTs increased, so did the delays in getting these custom glass components made. This is where Tektronix decided to use its existing expertise with ceramic strips during the pre-PCB era to create ceramic funnels for ceramic CRTs, as described in this 1967 video.

The Tektronix ceramic CRT molds underneath Building 13.
The Tektronix ceramic CRT molds underneath Building 13.

Recently, underneath Building 13 at the Tektronix campus, a ‘catacomb’ full of the molds for these funnels was discovered, covering a wide range of CRT types, including some round ones that were presumably made for military purposes, such as radar installations. These molds consist out of an inner part  (the mandrel) made from 7075-T6 aluminium, and an outer cast polyurethane boot. The ceramic (forsterite) powder is then formed under high pressure into the ceramic funnel, which is then fired in a kiln before a full inspection and assembly into a full CRT, including the phosphor-coated glass front section and rear section with the electron guns.

The advantages of ceramic funnels over glass ones are many, including the former being much harder and resilient to impact forces, while offering a lot of strength for thinner, lighter structures, all of which is desirable in (portable) lab equipment. Although LCDs would inevitably take over from CRTs here as well, these ceramic CRTs formed an integral part of Tektronix’s products, with every part of production handled in-house.

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Inside A Current Probe

[The Signal Path] had two Tektronix AC/DC current probes that didn’t work. Of course, that’s a great excuse to tear them open and try to get at least one working. You can see how it went in the video below. The symptoms differed between the two units, and along the way, the theory behind these probes needs some exploration.

The basic idea is simple, but, of course, the devil is in the details. A simple transformer doesn’t work well at high frequencies and won’t work at all at DC. The solution is to use a hall effect sensor to measure DC and also to feed it back to cancel coil saturation.

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OScope Advert From 1987 Rocks It

We can’t remember ever seeing a late-night TV ad for oscilloscopes before but, for some reason, Tektronix did produce a video ad in 1987. You can see it below and enjoy the glorious music and video production standards of the 1980s.

We assume this was made to show at some trade show or the like. Even if there was a Home Shopping Network in 1987, we doubt many of these would have been sold despite the assertion they were “low cost” — clearly a relative term in this case.

You’ve got to wonder if the narrator understood what he was saying or if he was just reading from a script. Pretty impressive either way. We loved these old scopes, although we also like having very capable scopes that don’t strain our backs to lift.

On the bright side, these scopes today are pretty affordable on the used market if you can find one that doesn’t need a repair with an exotic part. For example, we found several 2221s or 2221As for under $200 without looking hard. The shipping, of course, could potentially almost double the price.

While you can get a modern scope for $200, it probably isn’t the same quality as a Tektronix. Then again, the new scope won’t have CRTs and exotic Tektronix parts to wear out, either. Picking a scope is a pretty personal affair, though, so one person’s great scope might be another person’s piece of junk.

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USB Meets Core Memory In A Vintage ‘Scope

It’s normal today for even relatively modest instruments to have some form of computer control capability over Ethernet or USB. But five decades ago this was by no means a given, and when Tektronix shipped their P7001 digitiser module for their high-end oscilloscopes in 1971, they were initially designed to interface with a minicomputer. Not everybody has a PDP/11 lying around in 2023, but [Holger Lübben] wasn’t fazed by this. He set about creating a USB interface for this ancient piece of test equipment.

At its heart is a Teensy 4.1 which does the job of interfacing with the Tektronix 16-bit bus through a level shifting transceiver. The software for the Teensy comes with some demos, but sadly not the Tek BASIC of the original. We’re particularly impressed with the care to make the card frame for the module resemble as closely as possible an original Tektronix product.

We’re guessing very few of you will have this ancient test module on your bench, but the depth into which he goes over its internal design and programming makes this very much worth a read. If you fancy more vintage Tek goodness, take a look at this current probe.

Laser-Engraving Hairlines: When A Line Isn’t A Line

When is a line not a line? When it’s a series of tiny dots, of course!

The line is actually tiny, laser-etched craters, 0.25 mm center-to-center.

That’s the technique [Ed Nisley] used to create a super-fine, colored hairline in a piece of clear plastic — all part of his project to re-create a classic Tektronix analog calculator from the 1960s, but more on that in a moment.

[Ed] tried a variety of methods and techniques, including laser engraving a solid line, and milling a line with an extremely tiny v-tool. Results were serviceable, but what really did the trick was a series of tiny laser-etched craters filled in with a red marker. That resulted in what appears — to the naked eye — as an extremely fine hairline. But when magnified, as shown here, one can see it is really a series of small craters. The color comes from coloring in the line with a red marker, then wiping the excess off with some alcohol. The remaining pigment sitting in the craters gives just the right amount of color.

This is all part of [Ed]’s efforts to re-create the Tektronix Circuit Computer, a circular slide rule capable of calculating all kinds of useful electrical engineering-related things. And if you find yourself looking to design and build your own circular slide rule from scratch? We have you covered.

Cardboard Models Trace Design Process Of Vintage Tektronix Miniscopes

There aren’t many brands that inspire the kind of passion and fervency among its customers as Tektronix does. The venerable Oregon-based manufacturer of top-end test equipment has produced more collectible gear over the last 75 years than just about anyone else.

Over that time they have had plenty of innovations, and in the 1970s they started looking into miniaturizing their flagship oscilloscopes. The vintageTEK museum, run by current and former employees, has a review of the design process of the 200 series of portable oscilloscopes that’s really interesting. At a time when scopes were portable in the way a packed suitcase is portable, making a useful instrument in a pocketable form factor was quite a challenge — even for big pockets.

The article goes into great detail on the back-and-forth between the industrial designers, with their endless stream of models, and the engineers who would actually have to stuff a working scope into whatever case they came up with. The models from the museum’s collection are wonderful bits of history and show where the industrial designers really pushed for some innovative designs.

Some of the models are clearly derived from the design of the big bench scopes, but some have innovative flip-down covers and other interesting elements that never made it to production. Most of the models are cardboard, but some were made of aluminum in the machine shop and sport the familiar “Tek blue” livery. But the pièce de résistance of the collection is a working engineering model of what would become the 200-series of miniscopes, a handmade prototype with a tiny round CRT and crudely labeled controls.

The vintageTEK museum sounds like another bucket-list stop for computer and technology history buffs. Tek has been doing things their own way for a long time, and stopping by the museum is sure to be a treat.

Thanks to [Tanner Bass] for the tip.

Inside A $30,000 8 GHz Scope

One of the best things about the Internet — especially the video part — is that you can get exposed to lots of things you might otherwise not be able to see. Take oscilloscopes, for example. If you were lucky, you might have one or two really nice instruments at work and you certainly weren’t going to be allowed to tear them open if they were working well. [The Signal Path], as a case in point, tears down a $30,000 MSO6 8 GHz oscilloscope.

Actually, the base price is not quite $30,000 but by the time you outfit one, you’ll probably break the $30K barrier. Compared to the scopes we usually get to use, these are very different. Sure, the screens are larger and denser, but looking at the circuit boards they look more like some sort of high-end computer than an oscilloscope. Of course, in a way, that’s exactly what it is.

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